diff options
Diffstat (limited to 'kernel/seccomp.c')
| -rw-r--r-- | kernel/seccomp.c | 2640 |
1 files changed, 2348 insertions, 292 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index b7a10048a32c..25f62867a16d 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0 /* * linux/kernel/seccomp.c * @@ -12,34 +13,203 @@ * Mode 2 allows user-defined system call filters in the form * of Berkeley Packet Filters/Linux Socket Filters. */ +#define pr_fmt(fmt) "seccomp: " fmt -#include <linux/atomic.h> +#include <linux/refcount.h> #include <linux/audit.h> #include <linux/compat.h> +#include <linux/coredump.h> +#include <linux/kmemleak.h> +#include <linux/nospec.h> +#include <linux/prctl.h> #include <linux/sched.h> +#include <linux/sched/task_stack.h> #include <linux/seccomp.h> +#include <linux/slab.h> +#include <linux/syscalls.h> +#include <linux/sysctl.h> + +#include <asm/syscall.h> -/* #define SECCOMP_DEBUG 1 */ +/* Not exposed in headers: strictly internal use only. */ +#define SECCOMP_MODE_DEAD (SECCOMP_MODE_FILTER + 1) #ifdef CONFIG_SECCOMP_FILTER -#include <asm/syscall.h> +#include <linux/file.h> #include <linux/filter.h> +#include <linux/pid.h> #include <linux/ptrace.h> -#include <linux/security.h> -#include <linux/slab.h> -#include <linux/tracehook.h> +#include <linux/capability.h> #include <linux/uaccess.h> +#include <linux/anon_inodes.h> +#include <linux/lockdep.h> + +/* + * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the + * wrong direction flag in the ioctl number. This is the broken one, + * which the kernel needs to keep supporting until all userspaces stop + * using the wrong command number. + */ +#define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR SECCOMP_IOR(2, __u64) + +enum notify_state { + SECCOMP_NOTIFY_INIT, + SECCOMP_NOTIFY_SENT, + SECCOMP_NOTIFY_REPLIED, +}; + +struct seccomp_knotif { + /* The struct pid of the task whose filter triggered the notification */ + struct task_struct *task; + + /* The "cookie" for this request; this is unique for this filter. */ + u64 id; + + /* + * The seccomp data. This pointer is valid the entire time this + * notification is active, since it comes from __seccomp_filter which + * eclipses the entire lifecycle here. + */ + const struct seccomp_data *data; + + /* + * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a + * struct seccomp_knotif is created and starts out in INIT. Once the + * handler reads the notification off of an FD, it transitions to SENT. + * If a signal is received the state transitions back to INIT and + * another message is sent. When the userspace handler replies, state + * transitions to REPLIED. + */ + enum notify_state state; + + /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */ + int error; + long val; + u32 flags; + + /* + * Signals when this has changed states, such as the listener + * dying, a new seccomp addfd message, or changing to REPLIED + */ + struct completion ready; + + struct list_head list; + + /* outstanding addfd requests */ + struct list_head addfd; +}; + +/** + * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages + * + * @file: A reference to the file to install in the other task + * @fd: The fd number to install it at. If the fd number is -1, it means the + * installing process should allocate the fd as normal. + * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC + * is allowed. + * @ioctl_flags: The flags used for the seccomp_addfd ioctl. + * @setfd: whether or not SECCOMP_ADDFD_FLAG_SETFD was set during notify_addfd + * @ret: The return value of the installing process. It is set to the fd num + * upon success (>= 0). + * @completion: Indicates that the installing process has completed fd + * installation, or gone away (either due to successful + * reply, or signal) + * @list: list_head for chaining seccomp_kaddfd together. + * + */ +struct seccomp_kaddfd { + struct file *file; + int fd; + unsigned int flags; + __u32 ioctl_flags; + + union { + bool setfd; + /* To only be set on reply */ + int ret; + }; + struct completion completion; + struct list_head list; +}; + +/** + * struct notification - container for seccomp userspace notifications. Since + * most seccomp filters will not have notification listeners attached and this + * structure is fairly large, we store the notification-specific stuff in a + * separate structure. + * + * @requests: A semaphore that users of this notification can wait on for + * changes. Actual reads and writes are still controlled with + * filter->notify_lock. + * @flags: A set of SECCOMP_USER_NOTIF_FD_* flags. + * @next_id: The id of the next request. + * @notifications: A list of struct seccomp_knotif elements. + */ + +struct notification { + atomic_t requests; + u32 flags; + u64 next_id; + struct list_head notifications; +}; + +#ifdef SECCOMP_ARCH_NATIVE +/** + * struct action_cache - per-filter cache of seccomp actions per + * arch/syscall pair + * + * @allow_native: A bitmap where each bit represents whether the + * filter will always allow the syscall, for the + * native architecture. + * @allow_compat: A bitmap where each bit represents whether the + * filter will always allow the syscall, for the + * compat architecture. + */ +struct action_cache { + DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR); +#ifdef SECCOMP_ARCH_COMPAT + DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR); +#endif +}; +#else +struct action_cache { }; + +static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter, + const struct seccomp_data *sd) +{ + return false; +} + +static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter) +{ +} +#endif /* SECCOMP_ARCH_NATIVE */ /** * struct seccomp_filter - container for seccomp BPF programs * - * @usage: reference count to manage the object lifetime. - * get/put helpers should be used when accessing an instance - * outside of a lifetime-guarded section. In general, this - * is only needed for handling filters shared across tasks. + * @refs: Reference count to manage the object lifetime. + * A filter's reference count is incremented for each directly + * attached task, once for the dependent filter, and if + * requested for the user notifier. When @refs reaches zero, + * the filter can be freed. + * @users: A filter's @users count is incremented for each directly + * attached task (filter installation, fork(), thread_sync), + * and once for the dependent filter (tracked in filter->prev). + * When it reaches zero it indicates that no direct or indirect + * users of that filter exist. No new tasks can get associated with + * this filter after reaching 0. The @users count is always smaller + * or equal to @refs. Hence, reaching 0 for @users does not mean + * the filter can be freed. + * @cache: cache of arch/syscall mappings to actions + * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged + * @wait_killable_recv: Put notifying process in killable state once the + * notification is received by the userspace listener. * @prev: points to a previously installed, or inherited, filter - * @len: the number of instructions in the program - * @insns: the BPF program instructions to evaluate + * @prog: the BPF program to evaluate + * @notif: the struct that holds all notification related information + * @notify_lock: A lock for all notification-related accesses. + * @wqh: A wait queue for poll if a notifier is in use. * * seccomp_filter objects are organized in a tree linked via the @prev * pointer. For any task, it appears to be a singly-linked list starting @@ -49,66 +219,48 @@ * how namespaces work. * * seccomp_filter objects should never be modified after being attached - * to a task_struct (other than @usage). + * to a task_struct (other than @refs). */ struct seccomp_filter { - atomic_t usage; + refcount_t refs; + refcount_t users; + bool log; + bool wait_killable_recv; + struct action_cache cache; struct seccomp_filter *prev; - unsigned short len; /* Instruction count */ - struct sock_filter insns[]; + struct bpf_prog *prog; + struct notification *notif; + struct mutex notify_lock; + wait_queue_head_t wqh; }; /* Limit any path through the tree to 256KB worth of instructions. */ #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) -/** - * get_u32 - returns a u32 offset into data - * @data: a unsigned 64 bit value - * @index: 0 or 1 to return the first or second 32-bits - * - * This inline exists to hide the length of unsigned long. If a 32-bit - * unsigned long is passed in, it will be extended and the top 32-bits will be - * 0. If it is a 64-bit unsigned long, then whatever data is resident will be - * properly returned. - * +/* * Endianness is explicitly ignored and left for BPF program authors to manage * as per the specific architecture. */ -static inline u32 get_u32(u64 data, int index) +static void populate_seccomp_data(struct seccomp_data *sd) { - return ((u32 *)&data)[index]; -} + /* + * Instead of using current_pt_reg(), we're already doing the work + * to safely fetch "current", so just use "task" everywhere below. + */ + struct task_struct *task = current; + struct pt_regs *regs = task_pt_regs(task); + unsigned long args[6]; -/* Helper for bpf_load below. */ -#define BPF_DATA(_name) offsetof(struct seccomp_data, _name) -/** - * bpf_load: checks and returns a pointer to the requested offset - * @off: offset into struct seccomp_data to load from - * - * Returns the requested 32-bits of data. - * seccomp_check_filter() should assure that @off is 32-bit aligned - * and not out of bounds. Failure to do so is a BUG. - */ -u32 seccomp_bpf_load(int off) -{ - struct pt_regs *regs = task_pt_regs(current); - if (off == BPF_DATA(nr)) - return syscall_get_nr(current, regs); - if (off == BPF_DATA(arch)) - return syscall_get_arch(current, regs); - if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) { - unsigned long value; - int arg = (off - BPF_DATA(args[0])) / sizeof(u64); - int index = !!(off % sizeof(u64)); - syscall_get_arguments(current, regs, arg, 1, &value); - return get_u32(value, index); - } - if (off == BPF_DATA(instruction_pointer)) - return get_u32(KSTK_EIP(current), 0); - if (off == BPF_DATA(instruction_pointer) + sizeof(u32)) - return get_u32(KSTK_EIP(current), 1); - /* seccomp_check_filter should make this impossible. */ - BUG(); + sd->nr = syscall_get_nr(task, regs); + sd->arch = syscall_get_arch(task); + syscall_get_arguments(task, regs, args); + sd->args[0] = args[0]; + sd->args[1] = args[1]; + sd->args[2] = args[2]; + sd->args[3] = args[3]; + sd->args[4] = args[4]; + sd->args[5] = args[5]; + sd->instruction_pointer = KSTK_EIP(task); } /** @@ -116,7 +268,7 @@ u32 seccomp_bpf_load(int off) * @filter: filter to verify * @flen: length of filter * - * Takes a previously checked filter (by sk_chk_filter) and + * Takes a previously checked filter (by bpf_check_classic) and * redirects all filter code that loads struct sk_buff data * and related data through seccomp_bpf_load. It also * enforces length and alignment checking of those loads. @@ -132,59 +284,59 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) u32 k = ftest->k; switch (code) { - case BPF_S_LD_W_ABS: - ftest->code = BPF_S_ANC_SECCOMP_LD_W; + case BPF_LD | BPF_W | BPF_ABS: + ftest->code = BPF_LDX | BPF_W | BPF_ABS; /* 32-bit aligned and not out of bounds. */ if (k >= sizeof(struct seccomp_data) || k & 3) return -EINVAL; continue; - case BPF_S_LD_W_LEN: - ftest->code = BPF_S_LD_IMM; + case BPF_LD | BPF_W | BPF_LEN: + ftest->code = BPF_LD | BPF_IMM; ftest->k = sizeof(struct seccomp_data); continue; - case BPF_S_LDX_W_LEN: - ftest->code = BPF_S_LDX_IMM; + case BPF_LDX | BPF_W | BPF_LEN: + ftest->code = BPF_LDX | BPF_IMM; ftest->k = sizeof(struct seccomp_data); continue; /* Explicitly include allowed calls. */ - case BPF_S_RET_K: - case BPF_S_RET_A: - case BPF_S_ALU_ADD_K: - case BPF_S_ALU_ADD_X: - case BPF_S_ALU_SUB_K: - case BPF_S_ALU_SUB_X: - case BPF_S_ALU_MUL_K: - case BPF_S_ALU_MUL_X: - case BPF_S_ALU_DIV_X: - case BPF_S_ALU_AND_K: - case BPF_S_ALU_AND_X: - case BPF_S_ALU_OR_K: - case BPF_S_ALU_OR_X: - case BPF_S_ALU_XOR_K: - case BPF_S_ALU_XOR_X: - case BPF_S_ALU_LSH_K: - case BPF_S_ALU_LSH_X: - case BPF_S_ALU_RSH_K: - case BPF_S_ALU_RSH_X: - case BPF_S_ALU_NEG: - case BPF_S_LD_IMM: - case BPF_S_LDX_IMM: - case BPF_S_MISC_TAX: - case BPF_S_MISC_TXA: - case BPF_S_ALU_DIV_K: - case BPF_S_LD_MEM: - case BPF_S_LDX_MEM: - case BPF_S_ST: - case BPF_S_STX: - case BPF_S_JMP_JA: - case BPF_S_JMP_JEQ_K: - case BPF_S_JMP_JEQ_X: - case BPF_S_JMP_JGE_K: - case BPF_S_JMP_JGE_X: - case BPF_S_JMP_JGT_K: - case BPF_S_JMP_JGT_X: - case BPF_S_JMP_JSET_K: - case BPF_S_JMP_JSET_X: + case BPF_RET | BPF_K: + case BPF_RET | BPF_A: + case BPF_ALU | BPF_ADD | BPF_K: + case BPF_ALU | BPF_ADD | BPF_X: + case BPF_ALU | BPF_SUB | BPF_K: + case BPF_ALU | BPF_SUB | BPF_X: + case BPF_ALU | BPF_MUL | BPF_K: + case BPF_ALU | BPF_MUL | BPF_X: + case BPF_ALU | BPF_DIV | BPF_K: + case BPF_ALU | BPF_DIV | BPF_X: + case BPF_ALU | BPF_AND | BPF_K: + case BPF_ALU | BPF_AND | BPF_X: + case BPF_ALU | BPF_OR | BPF_K: + case BPF_ALU | BPF_OR | BPF_X: + case BPF_ALU | BPF_XOR | BPF_K: + case BPF_ALU | BPF_XOR | BPF_X: + case BPF_ALU | BPF_LSH | BPF_K: + case BPF_ALU | BPF_LSH | BPF_X: + case BPF_ALU | BPF_RSH | BPF_K: + case BPF_ALU | BPF_RSH | BPF_X: + case BPF_ALU | BPF_NEG: + case BPF_LD | BPF_IMM: + case BPF_LDX | BPF_IMM: + case BPF_MISC | BPF_TAX: + case BPF_MISC | BPF_TXA: + case BPF_LD | BPF_MEM: + case BPF_LDX | BPF_MEM: + case BPF_ST: + case BPF_STX: + case BPF_JMP | BPF_JA: + case BPF_JMP | BPF_JEQ | BPF_K: + case BPF_JMP | BPF_JEQ | BPF_X: + case BPF_JMP | BPF_JGE | BPF_K: + case BPF_JMP | BPF_JGE | BPF_X: + case BPF_JMP | BPF_JGT | BPF_K: + case BPF_JMP | BPF_JGT | BPF_X: + case BPF_JMP | BPF_JSET | BPF_K: + case BPF_JMP | BPF_JSET | BPF_X: continue; default: return -EINVAL; @@ -193,113 +345,387 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) return 0; } +#ifdef SECCOMP_ARCH_NATIVE +static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap, + size_t bitmap_size, + int syscall_nr) +{ + if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size)) + return false; + syscall_nr = array_index_nospec(syscall_nr, bitmap_size); + + return test_bit(syscall_nr, bitmap); +} + +/** + * seccomp_cache_check_allow - lookup seccomp cache + * @sfilter: The seccomp filter + * @sd: The seccomp data to lookup the cache with + * + * Returns true if the seccomp_data is cached and allowed. + */ +static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter, + const struct seccomp_data *sd) +{ + int syscall_nr = sd->nr; + const struct action_cache *cache = &sfilter->cache; + +#ifndef SECCOMP_ARCH_COMPAT + /* A native-only architecture doesn't need to check sd->arch. */ + return seccomp_cache_check_allow_bitmap(cache->allow_native, + SECCOMP_ARCH_NATIVE_NR, + syscall_nr); +#else + if (likely(sd->arch == SECCOMP_ARCH_NATIVE)) + return seccomp_cache_check_allow_bitmap(cache->allow_native, + SECCOMP_ARCH_NATIVE_NR, + syscall_nr); + if (likely(sd->arch == SECCOMP_ARCH_COMPAT)) + return seccomp_cache_check_allow_bitmap(cache->allow_compat, + SECCOMP_ARCH_COMPAT_NR, + syscall_nr); +#endif /* SECCOMP_ARCH_COMPAT */ + + WARN_ON_ONCE(true); + return false; +} +#endif /* SECCOMP_ARCH_NATIVE */ + +#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL))) /** - * seccomp_run_filters - evaluates all seccomp filters against @syscall - * @syscall: number of the current system call + * seccomp_run_filters - evaluates all seccomp filters against @sd + * @sd: optional seccomp data to be passed to filters + * @match: stores struct seccomp_filter that resulted in the return value, + * unless filter returned SECCOMP_RET_ALLOW, in which case it will + * be unchanged. * * Returns valid seccomp BPF response codes. */ -static u32 seccomp_run_filters(int syscall) +static u32 seccomp_run_filters(const struct seccomp_data *sd, + struct seccomp_filter **match) { - struct seccomp_filter *f; u32 ret = SECCOMP_RET_ALLOW; + /* Make sure cross-thread synced filter points somewhere sane. */ + struct seccomp_filter *f = + READ_ONCE(current->seccomp.filter); /* Ensure unexpected behavior doesn't result in failing open. */ - if (WARN_ON(current->seccomp.filter == NULL)) - return SECCOMP_RET_KILL; + if (WARN_ON(f == NULL)) + return SECCOMP_RET_KILL_PROCESS; + + if (seccomp_cache_check_allow(f, sd)) + return SECCOMP_RET_ALLOW; /* * All filters in the list are evaluated and the lowest BPF return * value always takes priority (ignoring the DATA). */ - for (f = current->seccomp.filter; f; f = f->prev) { - u32 cur_ret = sk_run_filter(NULL, f->insns); - if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) + for (; f; f = f->prev) { + u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd); + + if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { ret = cur_ret; + *match = f; + } } return ret; } +#endif /* CONFIG_SECCOMP_FILTER */ + +static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) +{ + assert_spin_locked(¤t->sighand->siglock); + + if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) + return false; + + return true; +} + +void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } + +static inline void seccomp_assign_mode(struct task_struct *task, + unsigned long seccomp_mode, + unsigned long flags) +{ + assert_spin_locked(&task->sighand->siglock); + + task->seccomp.mode = seccomp_mode; + /* + * Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and + * filter) is set. + */ + smp_mb__before_atomic(); + /* Assume default seccomp processes want spec flaw mitigation. */ + if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) + arch_seccomp_spec_mitigate(task); + set_task_syscall_work(task, SECCOMP); +} + +#ifdef CONFIG_SECCOMP_FILTER +/* Returns 1 if the parent is an ancestor of the child. */ +static int is_ancestor(struct seccomp_filter *parent, + struct seccomp_filter *child) +{ + /* NULL is the root ancestor. */ + if (parent == NULL) + return 1; + for (; child; child = child->prev) + if (child == parent) + return 1; + return 0; +} /** - * seccomp_attach_filter: Attaches a seccomp filter to current. + * seccomp_can_sync_threads: checks if all threads can be synchronized + * + * Expects sighand and cred_guard_mutex locks to be held. + * + * Returns 0 on success, -ve on error, or the pid of a thread which was + * either not in the correct seccomp mode or did not have an ancestral + * seccomp filter. + */ +static inline pid_t seccomp_can_sync_threads(void) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + assert_spin_locked(¤t->sighand->siglock); + + /* Validate all threads being eligible for synchronization. */ + caller = current; + for_each_thread(caller, thread) { + pid_t failed; + + /* Skip current, since it is initiating the sync. */ + if (thread == caller) + continue; + /* Skip exited threads. */ + if (thread->flags & PF_EXITING) + continue; + + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || + (thread->seccomp.mode == SECCOMP_MODE_FILTER && + is_ancestor(thread->seccomp.filter, + caller->seccomp.filter))) + continue; + + /* Return the first thread that cannot be synchronized. */ + failed = task_pid_vnr(thread); + /* If the pid cannot be resolved, then return -ESRCH */ + if (WARN_ON(failed == 0)) + failed = -ESRCH; + return failed; + } + + return 0; +} + +static inline void seccomp_filter_free(struct seccomp_filter *filter) +{ + if (filter) { + bpf_prog_destroy(filter->prog); + kfree(filter); + } +} + +static void __seccomp_filter_orphan(struct seccomp_filter *orig) +{ + while (orig && refcount_dec_and_test(&orig->users)) { + if (waitqueue_active(&orig->wqh)) + wake_up_poll(&orig->wqh, EPOLLHUP); + orig = orig->prev; + } +} + +static void __put_seccomp_filter(struct seccomp_filter *orig) +{ + /* Clean up single-reference branches iteratively. */ + while (orig && refcount_dec_and_test(&orig->refs)) { + struct seccomp_filter *freeme = orig; + orig = orig->prev; + seccomp_filter_free(freeme); + } +} + +static void __seccomp_filter_release(struct seccomp_filter *orig) +{ + /* Notify about any unused filters in the task's former filter tree. */ + __seccomp_filter_orphan(orig); + /* Finally drop all references to the task's former tree. */ + __put_seccomp_filter(orig); +} + +/** + * seccomp_filter_release - Detach the task from its filter tree, + * drop its reference count, and notify + * about unused filters + * + * @tsk: task the filter should be released from. + * + * This function should only be called when the task is exiting as + * it detaches it from its filter tree. PF_EXITING has to be set + * for the task. + */ +void seccomp_filter_release(struct task_struct *tsk) +{ + struct seccomp_filter *orig; + + if (WARN_ON((tsk->flags & PF_EXITING) == 0)) + return; + + if (READ_ONCE(tsk->seccomp.filter) == NULL) + return; + + spin_lock_irq(&tsk->sighand->siglock); + orig = tsk->seccomp.filter; + /* Detach task from its filter tree. */ + tsk->seccomp.filter = NULL; + spin_unlock_irq(&tsk->sighand->siglock); + __seccomp_filter_release(orig); +} + +/** + * seccomp_sync_threads: sets all threads to use current's filter + * + * @flags: SECCOMP_FILTER_FLAG_* flags to set during sync. + * + * Expects sighand and cred_guard_mutex locks to be held, and for + * seccomp_can_sync_threads() to have returned success already + * without dropping the locks. + * + */ +static inline void seccomp_sync_threads(unsigned long flags) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + assert_spin_locked(¤t->sighand->siglock); + + /* + * Don't touch any of the threads if the process is being killed. + * This allows for a lockless check in seccomp_filter_release. + */ + if (current->signal->flags & SIGNAL_GROUP_EXIT) + return; + + /* Synchronize all threads. */ + caller = current; + for_each_thread(caller, thread) { + /* Skip current, since it needs no changes. */ + if (thread == caller) + continue; + + /* + * Skip exited threads. seccomp_filter_release could have + * been already called for this task. + */ + if (thread->flags & PF_EXITING) + continue; + + /* Get a task reference for the new leaf node. */ + get_seccomp_filter(caller); + + /* + * Drop the task reference to the shared ancestor since + * current's path will hold a reference. (This also + * allows a put before the assignment.) + */ + __seccomp_filter_release(thread->seccomp.filter); + + /* Make our new filter tree visible. */ + smp_store_release(&thread->seccomp.filter, + caller->seccomp.filter); + atomic_set(&thread->seccomp.filter_count, + atomic_read(&caller->seccomp.filter_count)); + + /* + * Don't let an unprivileged task work around + * the no_new_privs restriction by creating + * a thread that sets it up, enters seccomp, + * then dies. + */ + if (task_no_new_privs(caller)) + task_set_no_new_privs(thread); + + /* + * Opt the other thread into seccomp if needed. + * As threads are considered to be trust-realm + * equivalent (see ptrace_may_access), it is safe to + * allow one thread to transition the other. + */ + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) + seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, + flags); + } +} + +/** + * seccomp_prepare_filter: Prepares a seccomp filter for use. * @fprog: BPF program to install * - * Returns 0 on success or an errno on failure. + * Returns filter on success or an ERR_PTR on failure. */ -static long seccomp_attach_filter(struct sock_fprog *fprog) +static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) { - struct seccomp_filter *filter; - unsigned long fp_size = fprog->len * sizeof(struct sock_filter); - unsigned long total_insns = fprog->len; - long ret; + struct seccomp_filter *sfilter; + int ret; + const bool save_orig = +#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE) + true; +#else + false; +#endif if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) - return -EINVAL; + return ERR_PTR(-EINVAL); - for (filter = current->seccomp.filter; filter; filter = filter->prev) - total_insns += filter->len + 4; /* include a 4 instr penalty */ - if (total_insns > MAX_INSNS_PER_PATH) - return -ENOMEM; + BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); /* - * Installing a seccomp filter requires that the task have + * Installing a seccomp filter requires that the task has * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. * This avoids scenarios where unprivileged tasks can affect the * behavior of privileged children. */ - if (!current->no_new_privs && - security_capable_noaudit(current_cred(), current_user_ns(), - CAP_SYS_ADMIN) != 0) - return -EACCES; + if (!task_no_new_privs(current) && + !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN)) + return ERR_PTR(-EACCES); /* Allocate a new seccomp_filter */ - filter = kzalloc(sizeof(struct seccomp_filter) + fp_size, - GFP_KERNEL|__GFP_NOWARN); - if (!filter) - return -ENOMEM; - atomic_set(&filter->usage, 1); - filter->len = fprog->len; - - /* Copy the instructions from fprog. */ - ret = -EFAULT; - if (copy_from_user(filter->insns, fprog->filter, fp_size)) - goto fail; + sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); + if (!sfilter) + return ERR_PTR(-ENOMEM); - /* Check and rewrite the fprog via the skb checker */ - ret = sk_chk_filter(filter->insns, filter->len); - if (ret) - goto fail; + mutex_init(&sfilter->notify_lock); + ret = bpf_prog_create_from_user(&sfilter->prog, fprog, + seccomp_check_filter, save_orig); + if (ret < 0) { + kfree(sfilter); + return ERR_PTR(ret); + } - /* Check and rewrite the fprog for seccomp use */ - ret = seccomp_check_filter(filter->insns, filter->len); - if (ret) - goto fail; + refcount_set(&sfilter->refs, 1); + refcount_set(&sfilter->users, 1); + init_waitqueue_head(&sfilter->wqh); - /* - * If there is an existing filter, make it the prev and don't drop its - * task reference. - */ - filter->prev = current->seccomp.filter; - current->seccomp.filter = filter; - return 0; -fail: - kfree(filter); - return ret; + return sfilter; } /** - * seccomp_attach_user_filter - attaches a user-supplied sock_fprog + * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog * @user_filter: pointer to the user data containing a sock_fprog. * * Returns 0 on success and non-zero otherwise. */ -long seccomp_attach_user_filter(char __user *user_filter) +static struct seccomp_filter * +seccomp_prepare_user_filter(const char __user *user_filter) { struct sock_fprog fprog; - long ret = -EFAULT; + struct seccomp_filter *filter = ERR_PTR(-EFAULT); #ifdef CONFIG_COMPAT - if (is_compat_task()) { + if (in_compat_syscall()) { struct compat_sock_fprog fprog32; if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) goto out; @@ -309,205 +735,1835 @@ long seccomp_attach_user_filter(char __user *user_filter) #endif if (copy_from_user(&fprog, user_filter, sizeof(fprog))) goto out; - ret = seccomp_attach_filter(&fprog); + filter = seccomp_prepare_filter(&fprog); out: - return ret; + return filter; } -/* get_seccomp_filter - increments the reference count of the filter on @tsk */ -void get_seccomp_filter(struct task_struct *tsk) +#ifdef SECCOMP_ARCH_NATIVE +static bool seccomp_uprobe_exception(struct seccomp_data *sd) { - struct seccomp_filter *orig = tsk->seccomp.filter; - if (!orig) - return; - /* Reference count is bounded by the number of total processes. */ - atomic_inc(&orig->usage); +#if defined __NR_uretprobe || defined __NR_uprobe +#ifdef SECCOMP_ARCH_COMPAT + if (sd->arch == SECCOMP_ARCH_NATIVE) +#endif + { +#ifdef __NR_uretprobe + if (sd->nr == __NR_uretprobe) + return true; +#endif +#ifdef __NR_uprobe + if (sd->nr == __NR_uprobe) + return true; +#endif + } +#endif + return false; } -/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ -void put_seccomp_filter(struct task_struct *tsk) +/** + * seccomp_is_const_allow - check if filter is constant allow with given data + * @fprog: The BPF programs + * @sd: The seccomp data to check against, only syscall number and arch + * number are considered constant. + */ +static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog, + struct seccomp_data *sd) { - struct seccomp_filter *orig = tsk->seccomp.filter; - /* Clean up single-reference branches iteratively. */ - while (orig && atomic_dec_and_test(&orig->usage)) { - struct seccomp_filter *freeme = orig; - orig = orig->prev; - kfree(freeme); + unsigned int reg_value = 0; + unsigned int pc; + bool op_res; + + if (WARN_ON_ONCE(!fprog)) + return false; + + /* Our single exception to filtering. */ + if (seccomp_uprobe_exception(sd)) + return true; + + for (pc = 0; pc < fprog->len; pc++) { + struct sock_filter *insn = &fprog->filter[pc]; + u16 code = insn->code; + u32 k = insn->k; + + switch (code) { + case BPF_LD | BPF_W | BPF_ABS: + switch (k) { + case offsetof(struct seccomp_data, nr): + reg_value = sd->nr; + break; + case offsetof(struct seccomp_data, arch): + reg_value = sd->arch; + break; + default: + /* can't optimize (non-constant value load) */ + return false; + } + break; + case BPF_RET | BPF_K: + /* reached return with constant values only, check allow */ + return k == SECCOMP_RET_ALLOW; + case BPF_JMP | BPF_JA: + pc += insn->k; + break; + case BPF_JMP | BPF_JEQ | BPF_K: + case BPF_JMP | BPF_JGE | BPF_K: + case BPF_JMP | BPF_JGT | BPF_K: + case BPF_JMP | BPF_JSET | BPF_K: + switch (BPF_OP(code)) { + case BPF_JEQ: + op_res = reg_value == k; + break; + case BPF_JGE: + op_res = reg_value >= k; + break; + case BPF_JGT: + op_res = reg_value > k; + break; + case BPF_JSET: + op_res = !!(reg_value & k); + break; + default: + /* can't optimize (unknown jump) */ + return false; + } + + pc += op_res ? insn->jt : insn->jf; + break; + case BPF_ALU | BPF_AND | BPF_K: + reg_value &= k; + break; + default: + /* can't optimize (unknown insn) */ + return false; + } + } + + /* ran off the end of the filter?! */ + WARN_ON(1); + return false; +} + +static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter, + void *bitmap, const void *bitmap_prev, + size_t bitmap_size, int arch) +{ + struct sock_fprog_kern *fprog = sfilter->prog->orig_prog; + struct seccomp_data sd; + int nr; + + if (bitmap_prev) { + /* The new filter must be as restrictive as the last. */ + bitmap_copy(bitmap, bitmap_prev, bitmap_size); + } else { + /* Before any filters, all syscalls are always allowed. */ + bitmap_fill(bitmap, bitmap_size); + } + + for (nr = 0; nr < bitmap_size; nr++) { + /* No bitmap change: not a cacheable action. */ + if (!test_bit(nr, bitmap)) + continue; + + sd.nr = nr; + sd.arch = arch; + + /* No bitmap change: continue to always allow. */ + if (seccomp_is_const_allow(fprog, &sd)) + continue; + + /* + * Not a cacheable action: always run filters. + * atomic clear_bit() not needed, filter not visible yet. + */ + __clear_bit(nr, bitmap); } } /** - * seccomp_send_sigsys - signals the task to allow in-process syscall emulation - * @syscall: syscall number to send to userland - * @reason: filter-supplied reason code to send to userland (via si_errno) + * seccomp_cache_prepare - emulate the filter to find cacheable syscalls + * @sfilter: The seccomp filter + * + * Returns 0 if successful or -errno if error occurred. + */ +static void seccomp_cache_prepare(struct seccomp_filter *sfilter) +{ + struct action_cache *cache = &sfilter->cache; + const struct action_cache *cache_prev = + sfilter->prev ? &sfilter->prev->cache : NULL; + + seccomp_cache_prepare_bitmap(sfilter, cache->allow_native, + cache_prev ? cache_prev->allow_native : NULL, + SECCOMP_ARCH_NATIVE_NR, + SECCOMP_ARCH_NATIVE); + +#ifdef SECCOMP_ARCH_COMPAT + seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat, + cache_prev ? cache_prev->allow_compat : NULL, + SECCOMP_ARCH_COMPAT_NR, + SECCOMP_ARCH_COMPAT); +#endif /* SECCOMP_ARCH_COMPAT */ +} +#endif /* SECCOMP_ARCH_NATIVE */ + +/** + * seccomp_attach_filter: validate and attach filter + * @flags: flags to change filter behavior + * @filter: seccomp filter to add to the current process + * + * Caller must be holding current->sighand->siglock lock. * - * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. + * Returns 0 on success, -ve on error, or + * - in TSYNC mode: the pid of a thread which was either not in the correct + * seccomp mode or did not have an ancestral seccomp filter + * - in NEW_LISTENER mode: the fd of the new listener */ -static void seccomp_send_sigsys(int syscall, int reason) -{ - struct siginfo info; - memset(&info, 0, sizeof(info)); - info.si_signo = SIGSYS; - info.si_code = SYS_SECCOMP; - info.si_call_addr = (void __user *)KSTK_EIP(current); - info.si_errno = reason; - info.si_arch = syscall_get_arch(current, task_pt_regs(current)); - info.si_syscall = syscall; - force_sig_info(SIGSYS, &info, current); +static long seccomp_attach_filter(unsigned int flags, + struct seccomp_filter *filter) +{ + unsigned long total_insns; + struct seccomp_filter *walker; + + assert_spin_locked(¤t->sighand->siglock); + + /* Validate resulting filter length. */ + total_insns = filter->prog->len; + for (walker = current->seccomp.filter; walker; walker = walker->prev) + total_insns += walker->prog->len + 4; /* 4 instr penalty */ + if (total_insns > MAX_INSNS_PER_PATH) + return -ENOMEM; + + /* If thread sync has been requested, check that it is possible. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) { + int ret; + + ret = seccomp_can_sync_threads(); + if (ret) { + if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) + return -ESRCH; + else + return ret; + } + } + + /* Set log flag, if present. */ + if (flags & SECCOMP_FILTER_FLAG_LOG) + filter->log = true; + + /* Set wait killable flag, if present. */ + if (flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) + filter->wait_killable_recv = true; + + /* + * If there is an existing filter, make it the prev and don't drop its + * task reference. + */ + filter->prev = current->seccomp.filter; + seccomp_cache_prepare(filter); + current->seccomp.filter = filter; + atomic_inc(¤t->seccomp.filter_count); + + /* Now that the new filter is in place, synchronize to all threads. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + seccomp_sync_threads(flags); + + return 0; +} + +static void __get_seccomp_filter(struct seccomp_filter *filter) +{ + refcount_inc(&filter->refs); +} + +/* get_seccomp_filter - increments the reference count of the filter on @tsk */ +void get_seccomp_filter(struct task_struct *tsk) +{ + struct seccomp_filter *orig = tsk->seccomp.filter; + if (!orig) + return; + __get_seccomp_filter(orig); + refcount_inc(&orig->users); } + #endif /* CONFIG_SECCOMP_FILTER */ +/* For use with seccomp_actions_logged */ +#define SECCOMP_LOG_KILL_PROCESS (1 << 0) +#define SECCOMP_LOG_KILL_THREAD (1 << 1) +#define SECCOMP_LOG_TRAP (1 << 2) +#define SECCOMP_LOG_ERRNO (1 << 3) +#define SECCOMP_LOG_TRACE (1 << 4) +#define SECCOMP_LOG_LOG (1 << 5) +#define SECCOMP_LOG_ALLOW (1 << 6) +#define SECCOMP_LOG_USER_NOTIF (1 << 7) + +static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | + SECCOMP_LOG_KILL_THREAD | + SECCOMP_LOG_TRAP | + SECCOMP_LOG_ERRNO | + SECCOMP_LOG_USER_NOTIF | + SECCOMP_LOG_TRACE | + SECCOMP_LOG_LOG; + +static inline void seccomp_log(unsigned long syscall, long signr, u32 action, + bool requested) +{ + bool log = false; + + switch (action) { + case SECCOMP_RET_ALLOW: + break; + case SECCOMP_RET_TRAP: + log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; + break; + case SECCOMP_RET_ERRNO: + log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; + break; + case SECCOMP_RET_TRACE: + log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; + break; + case SECCOMP_RET_USER_NOTIF: + log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF; + break; + case SECCOMP_RET_LOG: + log = seccomp_actions_logged & SECCOMP_LOG_LOG; + break; + case SECCOMP_RET_KILL_THREAD: + log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; + break; + case SECCOMP_RET_KILL_PROCESS: + default: + log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; + } + + /* + * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the + * FILTER_FLAG_LOG bit was set. The admin has the ability to silence + * any action from being logged by removing the action name from the + * seccomp_actions_logged sysctl. + */ + if (!log) + return; + + audit_seccomp(syscall, signr, action); +} + /* * Secure computing mode 1 allows only read/write/exit/sigreturn. * To be fully secure this must be combined with rlimit * to limit the stack allocations too. */ -static int mode1_syscalls[] = { +static const int mode1_syscalls[] = { __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, - 0, /* null terminated */ +#ifdef __NR_uretprobe + __NR_uretprobe, +#endif +#ifdef __NR_uprobe + __NR_uprobe, +#endif + -1, /* negative terminated */ }; +static void __secure_computing_strict(int this_syscall) +{ + const int *allowed_syscalls = mode1_syscalls; #ifdef CONFIG_COMPAT -static int mode1_syscalls_32[] = { - __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32, - 0, /* null terminated */ -}; + if (in_compat_syscall()) + allowed_syscalls = get_compat_mode1_syscalls(); #endif + do { + if (*allowed_syscalls == this_syscall) + return; + } while (*++allowed_syscalls != -1); -int __secure_computing(int this_syscall) +#ifdef SECCOMP_DEBUG + dump_stack(); +#endif + current->seccomp.mode = SECCOMP_MODE_DEAD; + seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); + do_exit(SIGKILL); +} + +#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER +void secure_computing_strict(int this_syscall) { int mode = current->seccomp.mode; - int exit_sig = 0; - int *syscall; - u32 ret; - switch (mode) { - case SECCOMP_MODE_STRICT: - syscall = mode1_syscalls; -#ifdef CONFIG_COMPAT - if (is_compat_task()) - syscall = mode1_syscalls_32; -#endif - do { - if (*syscall == this_syscall) - return 0; - } while (*++syscall); - exit_sig = SIGKILL; - ret = SECCOMP_RET_KILL; - break; + if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && + unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) + return; + + if (mode == SECCOMP_MODE_DISABLED) + return; + else if (mode == SECCOMP_MODE_STRICT) + __secure_computing_strict(this_syscall); + else + BUG(); +} +int __secure_computing(void) +{ + int this_syscall = syscall_get_nr(current, current_pt_regs()); + + secure_computing_strict(this_syscall); + return 0; +} +#else + #ifdef CONFIG_SECCOMP_FILTER - case SECCOMP_MODE_FILTER: { - int data; - struct pt_regs *regs = task_pt_regs(current); - ret = seccomp_run_filters(this_syscall); - data = ret & SECCOMP_RET_DATA; - ret &= SECCOMP_RET_ACTION; - switch (ret) { - case SECCOMP_RET_ERRNO: - /* Set the low-order 16-bits as a errno. */ - syscall_set_return_value(current, regs, - -data, 0); - goto skip; - case SECCOMP_RET_TRAP: - /* Show the handler the original registers. */ - syscall_rollback(current, regs); - /* Let the filter pass back 16 bits of data. */ - seccomp_send_sigsys(this_syscall, data); - goto skip; - case SECCOMP_RET_TRACE: - /* Skip these calls if there is no tracer. */ - if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { - syscall_set_return_value(current, regs, - -ENOSYS, 0); - goto skip; - } - /* Allow the BPF to provide the event message */ - ptrace_event(PTRACE_EVENT_SECCOMP, data); +static u64 seccomp_next_notify_id(struct seccomp_filter *filter) +{ + /* + * Note: overflow is ok here, the id just needs to be unique per + * filter. + */ + lockdep_assert_held(&filter->notify_lock); + return filter->notif->next_id++; +} + +static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n) +{ + int fd; + + /* + * Remove the notification, and reset the list pointers, indicating + * that it has been handled. + */ + list_del_init(&addfd->list); + if (!addfd->setfd) + fd = receive_fd(addfd->file, NULL, addfd->flags); + else + fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags); + addfd->ret = fd; + + if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) { + /* If we fail reset and return an error to the notifier */ + if (fd < 0) { + n->state = SECCOMP_NOTIFY_SENT; + } else { + /* Return the FD we just added */ + n->flags = 0; + n->error = 0; + n->val = fd; + } + } + + /* + * Mark the notification as completed. From this point, addfd mem + * might be invalidated and we can't safely read it anymore. + */ + complete(&addfd->completion); +} + +static bool should_sleep_killable(struct seccomp_filter *match, + struct seccomp_knotif *n) +{ + return match->wait_killable_recv && n->state >= SECCOMP_NOTIFY_SENT; +} + +static int seccomp_do_user_notification(int this_syscall, + struct seccomp_filter *match, + const struct seccomp_data *sd) +{ + int err; + u32 flags = 0; + long ret = 0; + struct seccomp_knotif n = {}; + struct seccomp_kaddfd *addfd, *tmp; + + mutex_lock(&match->notify_lock); + err = -ENOSYS; + if (!match->notif) + goto out; + + n.task = current; + n.state = SECCOMP_NOTIFY_INIT; + n.data = sd; + n.id = seccomp_next_notify_id(match); + init_completion(&n.ready); + list_add_tail(&n.list, &match->notif->notifications); + INIT_LIST_HEAD(&n.addfd); + + atomic_inc(&match->notif->requests); + if (match->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) + wake_up_poll_on_current_cpu(&match->wqh, EPOLLIN | EPOLLRDNORM); + else + wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM); + + /* + * This is where we wait for a reply from userspace. + */ + do { + bool wait_killable = should_sleep_killable(match, &n); + + mutex_unlock(&match->notify_lock); + if (wait_killable) + err = wait_for_completion_killable(&n.ready); + else + err = wait_for_completion_interruptible(&n.ready); + mutex_lock(&match->notify_lock); + + if (err != 0) { /* - * The delivery of a fatal signal during event - * notification may silently skip tracer notification. - * Terminating the task now avoids executing a system - * call that may not be intended. + * Check to see whether we should switch to wait + * killable. Only return the interrupted error if not. */ - if (fatal_signal_pending(current)) - break; - if (syscall_get_nr(current, regs) < 0) - goto skip; /* Explicit request to skip. */ + if (!(!wait_killable && should_sleep_killable(match, &n))) + goto interrupted; + } + addfd = list_first_entry_or_null(&n.addfd, + struct seccomp_kaddfd, list); + /* Check if we were woken up by a addfd message */ + if (addfd) + seccomp_handle_addfd(addfd, &n); + + } while (n.state != SECCOMP_NOTIFY_REPLIED); + + ret = n.val; + err = n.error; + flags = n.flags; + +interrupted: + /* If there were any pending addfd calls, clear them out */ + list_for_each_entry_safe(addfd, tmp, &n.addfd, list) { + /* The process went away before we got a chance to handle it */ + addfd->ret = -ESRCH; + list_del_init(&addfd->list); + complete(&addfd->completion); + } + + /* + * Note that it's possible the listener died in between the time when + * we were notified of a response (or a signal) and when we were able to + * re-acquire the lock, so only delete from the list if the + * notification actually exists. + * + * Also note that this test is only valid because there's no way to + * *reattach* to a notifier right now. If one is added, we'll need to + * keep track of the notif itself and make sure they match here. + */ + if (match->notif) + list_del(&n.list); +out: + mutex_unlock(&match->notify_lock); + + /* Userspace requests to continue the syscall. */ + if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) + return 0; + + syscall_set_return_value(current, current_pt_regs(), + err, ret); + return -1; +} + +static int __seccomp_filter(int this_syscall, const bool recheck_after_trace) +{ + u32 filter_ret, action; + struct seccomp_data sd; + struct seccomp_filter *match = NULL; + int data; + + /* + * Make sure that any changes to mode from another thread have + * been seen after SYSCALL_WORK_SECCOMP was seen. + */ + smp_rmb(); + + populate_seccomp_data(&sd); + + filter_ret = seccomp_run_filters(&sd, &match); + data = filter_ret & SECCOMP_RET_DATA; + action = filter_ret & SECCOMP_RET_ACTION_FULL; + + switch (action) { + case SECCOMP_RET_ERRNO: + /* Set low-order bits as an errno, capped at MAX_ERRNO. */ + if (data > MAX_ERRNO) + data = MAX_ERRNO; + syscall_set_return_value(current, current_pt_regs(), + -data, 0); + goto skip; + + case SECCOMP_RET_TRAP: + /* Show the handler the original registers. */ + syscall_rollback(current, current_pt_regs()); + /* Let the filter pass back 16 bits of data. */ + force_sig_seccomp(this_syscall, data, false); + goto skip; + + case SECCOMP_RET_TRACE: + /* We've been put in this state by the ptracer already. */ + if (recheck_after_trace) return 0; - case SECCOMP_RET_ALLOW: - return 0; - case SECCOMP_RET_KILL: - default: - break; + + /* ENOSYS these calls if there is no tracer attached. */ + if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { + syscall_set_return_value(current, + current_pt_regs(), + -ENOSYS, 0); + goto skip; } - exit_sig = SIGSYS; - break; + + /* Allow the BPF to provide the event message */ + ptrace_event(PTRACE_EVENT_SECCOMP, data); + /* + * The delivery of a fatal signal during event + * notification may silently skip tracer notification, + * which could leave us with a potentially unmodified + * syscall that the tracer would have liked to have + * changed. Since the process is about to die, we just + * force the syscall to be skipped and let the signal + * kill the process and correctly handle any tracer exit + * notifications. + */ + if (fatal_signal_pending(current)) + goto skip; + /* Check if the tracer forced the syscall to be skipped. */ + this_syscall = syscall_get_nr(current, current_pt_regs()); + if (this_syscall < 0) + goto skip; + + /* + * Recheck the syscall, since it may have changed. This + * intentionally uses a NULL struct seccomp_data to force + * a reload of all registers. This does not goto skip since + * a skip would have already been reported. + */ + if (__seccomp_filter(this_syscall, true)) + return -1; + + return 0; + + case SECCOMP_RET_USER_NOTIF: + if (seccomp_do_user_notification(this_syscall, match, &sd)) + goto skip; + + return 0; + + case SECCOMP_RET_LOG: + seccomp_log(this_syscall, 0, action, true); + return 0; + + case SECCOMP_RET_ALLOW: + /* + * Note that the "match" filter will always be NULL for + * this action since SECCOMP_RET_ALLOW is the starting + * state in seccomp_run_filters(). + */ + return 0; + + case SECCOMP_RET_KILL_THREAD: + case SECCOMP_RET_KILL_PROCESS: + default: + current->seccomp.mode = SECCOMP_MODE_DEAD; + seccomp_log(this_syscall, SIGSYS, action, true); + /* Dump core only if this is the last remaining thread. */ + if (action != SECCOMP_RET_KILL_THREAD || + (atomic_read(¤t->signal->live) == 1)) { + /* Show the original registers in the dump. */ + syscall_rollback(current, current_pt_regs()); + /* Trigger a coredump with SIGSYS */ + force_sig_seccomp(this_syscall, data, true); + } else { + do_exit(SIGSYS); + } + return -1; /* skip the syscall go directly to signal handling */ } + + unreachable(); + +skip: + seccomp_log(this_syscall, 0, action, match ? match->log : false); + return -1; +} +#else +static int __seccomp_filter(int this_syscall, const bool recheck_after_trace) +{ + BUG(); + + return -1; +} #endif + +int __secure_computing(void) +{ + int mode = current->seccomp.mode; + int this_syscall; + + if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && + unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) + return 0; + + this_syscall = syscall_get_nr(current, current_pt_regs()); + + switch (mode) { + case SECCOMP_MODE_STRICT: + __secure_computing_strict(this_syscall); /* may call do_exit */ + return 0; + case SECCOMP_MODE_FILTER: + return __seccomp_filter(this_syscall, false); + /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */ + case SECCOMP_MODE_DEAD: + WARN_ON_ONCE(1); + do_exit(SIGKILL); + return -1; default: BUG(); } +} +#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ -#ifdef SECCOMP_DEBUG - dump_stack(); +long prctl_get_seccomp(void) +{ + return current->seccomp.mode; +} + +/** + * seccomp_set_mode_strict: internal function for setting strict seccomp + * + * Once current->seccomp.mode is non-zero, it may not be changed. + * + * Returns 0 on success or -EINVAL on failure. + */ +static long seccomp_set_mode_strict(void) +{ + const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; + long ret = -EINVAL; + + spin_lock_irq(¤t->sighand->siglock); + + if (!seccomp_may_assign_mode(seccomp_mode)) + goto out; + +#ifdef TIF_NOTSC + disable_TSC(); #endif - audit_seccomp(this_syscall, exit_sig, ret); - do_exit(exit_sig); + seccomp_assign_mode(current, seccomp_mode, 0); + ret = 0; + +out: + spin_unlock_irq(¤t->sighand->siglock); + + return ret; +} + #ifdef CONFIG_SECCOMP_FILTER -skip: - audit_seccomp(this_syscall, exit_sig, ret); -#endif - return -1; +static void seccomp_notify_free(struct seccomp_filter *filter) +{ + kfree(filter->notif); + filter->notif = NULL; } -long prctl_get_seccomp(void) +static void seccomp_notify_detach(struct seccomp_filter *filter) { - return current->seccomp.mode; + struct seccomp_knotif *knotif; + + if (!filter) + return; + + mutex_lock(&filter->notify_lock); + + /* + * If this file is being closed because e.g. the task who owned it + * died, let's wake everyone up who was waiting on us. + */ + list_for_each_entry(knotif, &filter->notif->notifications, list) { + if (knotif->state == SECCOMP_NOTIFY_REPLIED) + continue; + + knotif->state = SECCOMP_NOTIFY_REPLIED; + knotif->error = -ENOSYS; + knotif->val = 0; + + /* + * We do not need to wake up any pending addfd messages, as + * the notifier will do that for us, as this just looks + * like a standard reply. + */ + complete(&knotif->ready); + } + + seccomp_notify_free(filter); + mutex_unlock(&filter->notify_lock); +} + +static int seccomp_notify_release(struct inode *inode, struct file *file) +{ + struct seccomp_filter *filter = file->private_data; + + seccomp_notify_detach(filter); + __put_seccomp_filter(filter); + return 0; +} + +/* must be called with notif_lock held */ +static inline struct seccomp_knotif * +find_notification(struct seccomp_filter *filter, u64 id) +{ + struct seccomp_knotif *cur; + + lockdep_assert_held(&filter->notify_lock); + + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->id == id) + return cur; + } + + return NULL; +} + +static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync, + void *key) +{ + /* Avoid a wakeup if event not interesting for us. */ + if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP))) + return 0; + return autoremove_wake_function(wait, mode, sync, key); +} + +static int recv_wait_event(struct seccomp_filter *filter) +{ + DEFINE_WAIT_FUNC(wait, recv_wake_function); + int ret; + + if (refcount_read(&filter->users) == 0) + return 0; + + if (atomic_dec_if_positive(&filter->notif->requests) >= 0) + return 0; + + for (;;) { + ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE); + + if (atomic_dec_if_positive(&filter->notif->requests) >= 0) + break; + if (refcount_read(&filter->users) == 0) + break; + + if (ret) + return ret; + + schedule(); + } + finish_wait(&filter->wqh, &wait); + return 0; +} + +static long seccomp_notify_recv(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_knotif *knotif = NULL, *cur; + struct seccomp_notif unotif; + ssize_t ret; + + /* Verify that we're not given garbage to keep struct extensible. */ + ret = check_zeroed_user(buf, sizeof(unotif)); + if (ret < 0) + return ret; + if (!ret) + return -EINVAL; + + memset(&unotif, 0, sizeof(unotif)); + + ret = recv_wait_event(filter); + if (ret < 0) + return ret; + + mutex_lock(&filter->notify_lock); + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->state == SECCOMP_NOTIFY_INIT) { + knotif = cur; + break; + } + } + + /* + * If we didn't find a notification, it could be that the task was + * interrupted by a fatal signal between the time we were woken and + * when we were able to acquire the rw lock. + */ + if (!knotif) { + ret = -ENOENT; + goto out; + } + + unotif.id = knotif->id; + unotif.pid = task_pid_vnr(knotif->task); + unotif.data = *(knotif->data); + + knotif->state = SECCOMP_NOTIFY_SENT; + wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM); + ret = 0; +out: + mutex_unlock(&filter->notify_lock); + + if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) { + ret = -EFAULT; + + /* + * Userspace screwed up. To make sure that we keep this + * notification alive, let's reset it back to INIT. It + * may have died when we released the lock, so we need to make + * sure it's still around. + */ + mutex_lock(&filter->notify_lock); + knotif = find_notification(filter, unotif.id); + if (knotif) { + /* Reset the process to make sure it's not stuck */ + if (should_sleep_killable(filter, knotif)) + complete(&knotif->ready); + knotif->state = SECCOMP_NOTIFY_INIT; + atomic_inc(&filter->notif->requests); + wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM); + } + mutex_unlock(&filter->notify_lock); + } + + return ret; +} + +static long seccomp_notify_send(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_notif_resp resp = {}; + struct seccomp_knotif *knotif; + long ret; + + if (copy_from_user(&resp, buf, sizeof(resp))) + return -EFAULT; + + if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE) + return -EINVAL; + + if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) && + (resp.error || resp.val)) + return -EINVAL; + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return ret; + + knotif = find_notification(filter, resp.id); + if (!knotif) { + ret = -ENOENT; + goto out; + } + + /* Allow exactly one reply. */ + if (knotif->state != SECCOMP_NOTIFY_SENT) { + ret = -EINPROGRESS; + goto out; + } + + ret = 0; + knotif->state = SECCOMP_NOTIFY_REPLIED; + knotif->error = resp.error; + knotif->val = resp.val; + knotif->flags = resp.flags; + if (filter->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) + complete_on_current_cpu(&knotif->ready); + else + complete(&knotif->ready); +out: + mutex_unlock(&filter->notify_lock); + return ret; +} + +static long seccomp_notify_id_valid(struct seccomp_filter *filter, + void __user *buf) +{ + struct seccomp_knotif *knotif; + u64 id; + long ret; + + if (copy_from_user(&id, buf, sizeof(id))) + return -EFAULT; + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return ret; + + knotif = find_notification(filter, id); + if (knotif && knotif->state == SECCOMP_NOTIFY_SENT) + ret = 0; + else + ret = -ENOENT; + + mutex_unlock(&filter->notify_lock); + return ret; +} + +static long seccomp_notify_set_flags(struct seccomp_filter *filter, + unsigned long flags) +{ + long ret; + + if (flags & ~SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) + return -EINVAL; + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + return ret; + filter->notif->flags = flags; + mutex_unlock(&filter->notify_lock); + return 0; +} + +static long seccomp_notify_addfd(struct seccomp_filter *filter, + struct seccomp_notif_addfd __user *uaddfd, + unsigned int size) +{ + struct seccomp_notif_addfd addfd; + struct seccomp_knotif *knotif; + struct seccomp_kaddfd kaddfd; + int ret; + + BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0); + BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST); + + if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE) + return -EINVAL; + + ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size); + if (ret) + return ret; + + if (addfd.newfd_flags & ~O_CLOEXEC) + return -EINVAL; + + if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND)) + return -EINVAL; + + if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD)) + return -EINVAL; + + kaddfd.file = fget(addfd.srcfd); + if (!kaddfd.file) + return -EBADF; + + kaddfd.ioctl_flags = addfd.flags; + kaddfd.flags = addfd.newfd_flags; + kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD; + kaddfd.fd = addfd.newfd; + init_completion(&kaddfd.completion); + + ret = mutex_lock_interruptible(&filter->notify_lock); + if (ret < 0) + goto out; + + knotif = find_notification(filter, addfd.id); + if (!knotif) { + ret = -ENOENT; + goto out_unlock; + } + + /* + * We do not want to allow for FD injection to occur before the + * notification has been picked up by a userspace handler, or after + * the notification has been replied to. + */ + if (knotif->state != SECCOMP_NOTIFY_SENT) { + ret = -EINPROGRESS; + goto out_unlock; + } + + if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) { + /* + * Disallow queuing an atomic addfd + send reply while there are + * some addfd requests still to process. + * + * There is no clear reason to support it and allows us to keep + * the loop on the other side straight-forward. + */ + if (!list_empty(&knotif->addfd)) { + ret = -EBUSY; + goto out_unlock; + } + + /* Allow exactly only one reply */ + knotif->state = SECCOMP_NOTIFY_REPLIED; + } + + list_add(&kaddfd.list, &knotif->addfd); + complete(&knotif->ready); + mutex_unlock(&filter->notify_lock); + + /* Now we wait for it to be processed or be interrupted */ + ret = wait_for_completion_interruptible(&kaddfd.completion); + if (ret == 0) { + /* + * We had a successful completion. The other side has already + * removed us from the addfd queue, and + * wait_for_completion_interruptible has a memory barrier upon + * success that lets us read this value directly without + * locking. + */ + ret = kaddfd.ret; + goto out; + } + + mutex_lock(&filter->notify_lock); + /* + * Even though we were woken up by a signal and not a successful + * completion, a completion may have happened in the mean time. + * + * We need to check again if the addfd request has been handled, + * and if not, we will remove it from the queue. + */ + if (list_empty(&kaddfd.list)) + ret = kaddfd.ret; + else + list_del(&kaddfd.list); + +out_unlock: + mutex_unlock(&filter->notify_lock); +out: + fput(kaddfd.file); + + return ret; +} + +static long seccomp_notify_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct seccomp_filter *filter = file->private_data; + void __user *buf = (void __user *)arg; + + /* Fixed-size ioctls */ + switch (cmd) { + case SECCOMP_IOCTL_NOTIF_RECV: + return seccomp_notify_recv(filter, buf); + case SECCOMP_IOCTL_NOTIF_SEND: + return seccomp_notify_send(filter, buf); + case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR: + case SECCOMP_IOCTL_NOTIF_ID_VALID: + return seccomp_notify_id_valid(filter, buf); + case SECCOMP_IOCTL_NOTIF_SET_FLAGS: + return seccomp_notify_set_flags(filter, arg); + } + + /* Extensible Argument ioctls */ +#define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK)) + switch (EA_IOCTL(cmd)) { + case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD): + return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd)); + default: + return -EINVAL; + } +} + +static __poll_t seccomp_notify_poll(struct file *file, + struct poll_table_struct *poll_tab) +{ + struct seccomp_filter *filter = file->private_data; + __poll_t ret = 0; + struct seccomp_knotif *cur; + + poll_wait(file, &filter->wqh, poll_tab); + + if (mutex_lock_interruptible(&filter->notify_lock) < 0) + return EPOLLERR; + + list_for_each_entry(cur, &filter->notif->notifications, list) { + if (cur->state == SECCOMP_NOTIFY_INIT) + ret |= EPOLLIN | EPOLLRDNORM; + if (cur->state == SECCOMP_NOTIFY_SENT) + ret |= EPOLLOUT | EPOLLWRNORM; + if ((ret & EPOLLIN) && (ret & EPOLLOUT)) + break; + } + + mutex_unlock(&filter->notify_lock); + + if (refcount_read(&filter->users) == 0) + ret |= EPOLLHUP; + + return ret; +} + +static const struct file_operations seccomp_notify_ops = { + .poll = seccomp_notify_poll, + .release = seccomp_notify_release, + .unlocked_ioctl = seccomp_notify_ioctl, + .compat_ioctl = seccomp_notify_ioctl, +}; + +static struct file *init_listener(struct seccomp_filter *filter) +{ + struct file *ret; + + ret = ERR_PTR(-ENOMEM); + filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); + if (!filter->notif) + goto out; + + filter->notif->next_id = get_random_u64(); + INIT_LIST_HEAD(&filter->notif->notifications); + + ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, + filter, O_RDWR); + if (IS_ERR(ret)) + goto out_notif; + + /* The file has a reference to it now */ + __get_seccomp_filter(filter); + +out_notif: + if (IS_ERR(ret)) + seccomp_notify_free(filter); +out: + return ret; +} + +/* + * Does @new_child have a listener while an ancestor also has a listener? + * If so, we'll want to reject this filter. + * This only has to be tested for the current process, even in the TSYNC case, + * because TSYNC installs @child with the same parent on all threads. + * Note that @new_child is not hooked up to its parent at this point yet, so + * we use current->seccomp.filter. + */ +static bool has_duplicate_listener(struct seccomp_filter *new_child) +{ + struct seccomp_filter *cur; + + /* must be protected against concurrent TSYNC */ + lockdep_assert_held(¤t->sighand->siglock); + + if (!new_child->notif) + return false; + for (cur = current->seccomp.filter; cur; cur = cur->prev) { + if (cur->notif) + return true; + } + + return false; } /** - * prctl_set_seccomp: configures current->seccomp.mode - * @seccomp_mode: requested mode to use - * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER + * seccomp_set_mode_filter: internal function for setting seccomp filter + * @flags: flags to change filter behavior + * @filter: struct sock_fprog containing filter * - * This function may be called repeatedly with a @seccomp_mode of - * SECCOMP_MODE_FILTER to install additional filters. Every filter - * successfully installed will be evaluated (in reverse order) for each system - * call the task makes. + * This function may be called repeatedly to install additional filters. + * Every filter successfully installed will be evaluated (in reverse order) + * for each system call the task makes. * * Once current->seccomp.mode is non-zero, it may not be changed. * * Returns 0 on success or -EINVAL on failure. */ -long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) +static long seccomp_set_mode_filter(unsigned int flags, + const char __user *filter) { + const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; + struct seccomp_filter *prepared = NULL; long ret = -EINVAL; + int listener = -1; + struct file *listener_f = NULL; + + /* Validate flags. */ + if (flags & ~SECCOMP_FILTER_FLAG_MASK) + return -EINVAL; - if (current->seccomp.mode && - current->seccomp.mode != seccomp_mode) + /* + * In the successful case, NEW_LISTENER returns the new listener fd. + * But in the failure case, TSYNC returns the thread that died. If you + * combine these two flags, there's no way to tell whether something + * succeeded or failed. So, let's disallow this combination if the user + * has not explicitly requested no errors from TSYNC. + */ + if ((flags & SECCOMP_FILTER_FLAG_TSYNC) && + (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) && + ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0)) + return -EINVAL; + + /* + * The SECCOMP_FILTER_FLAG_WAIT_KILLABLE_SENT flag doesn't make sense + * without the SECCOMP_FILTER_FLAG_NEW_LISTENER flag. + */ + if ((flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) && + ((flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) == 0)) + return -EINVAL; + + /* Prepare the new filter before holding any locks. */ + prepared = seccomp_prepare_user_filter(filter); + if (IS_ERR(prepared)) + return PTR_ERR(prepared); + + if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { + listener = get_unused_fd_flags(O_CLOEXEC); + if (listener < 0) { + ret = listener; + goto out_free; + } + + listener_f = init_listener(prepared); + if (IS_ERR(listener_f)) { + put_unused_fd(listener); + ret = PTR_ERR(listener_f); + goto out_free; + } + } + + /* + * Make sure we cannot change seccomp or nnp state via TSYNC + * while another thread is in the middle of calling exec. + */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC && + mutex_lock_killable(¤t->signal->cred_guard_mutex)) + goto out_put_fd; + + spin_lock_irq(¤t->sighand->siglock); + + if (!seccomp_may_assign_mode(seccomp_mode)) + goto out; + + if (has_duplicate_listener(prepared)) { + ret = -EBUSY; + goto out; + } + + ret = seccomp_attach_filter(flags, prepared); + if (ret) goto out; + /* Do not free the successfully attached filter. */ + prepared = NULL; + + seccomp_assign_mode(current, seccomp_mode, flags); +out: + spin_unlock_irq(¤t->sighand->siglock); + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + mutex_unlock(¤t->signal->cred_guard_mutex); +out_put_fd: + if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { + if (ret) { + listener_f->private_data = NULL; + fput(listener_f); + put_unused_fd(listener); + seccomp_notify_detach(prepared); + } else { + fd_install(listener, listener_f); + ret = listener; + } + } +out_free: + seccomp_filter_free(prepared); + return ret; +} +#else +static inline long seccomp_set_mode_filter(unsigned int flags, + const char __user *filter) +{ + return -EINVAL; +} +#endif + +static long seccomp_get_action_avail(const char __user *uaction) +{ + u32 action; + + if (copy_from_user(&action, uaction, sizeof(action))) + return -EFAULT; + + switch (action) { + case SECCOMP_RET_KILL_PROCESS: + case SECCOMP_RET_KILL_THREAD: + case SECCOMP_RET_TRAP: + case SECCOMP_RET_ERRNO: + case SECCOMP_RET_USER_NOTIF: + case SECCOMP_RET_TRACE: + case SECCOMP_RET_LOG: + case SECCOMP_RET_ALLOW: + break; + default: + return -EOPNOTSUPP; + } + + return 0; +} + +static long seccomp_get_notif_sizes(void __user *usizes) +{ + struct seccomp_notif_sizes sizes = { + .seccomp_notif = sizeof(struct seccomp_notif), + .seccomp_notif_resp = sizeof(struct seccomp_notif_resp), + .seccomp_data = sizeof(struct seccomp_data), + }; + + if (copy_to_user(usizes, &sizes, sizeof(sizes))) + return -EFAULT; + + return 0; +} + +/* Common entry point for both prctl and syscall. */ +static long do_seccomp(unsigned int op, unsigned int flags, + void __user *uargs) +{ + switch (op) { + case SECCOMP_SET_MODE_STRICT: + if (flags != 0 || uargs != NULL) + return -EINVAL; + return seccomp_set_mode_strict(); + case SECCOMP_SET_MODE_FILTER: + return seccomp_set_mode_filter(flags, uargs); + case SECCOMP_GET_ACTION_AVAIL: + if (flags != 0) + return -EINVAL; + + return seccomp_get_action_avail(uargs); + case SECCOMP_GET_NOTIF_SIZES: + if (flags != 0) + return -EINVAL; + + return seccomp_get_notif_sizes(uargs); + default: + return -EINVAL; + } +} + +SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, + void __user *, uargs) +{ + return do_seccomp(op, flags, uargs); +} + +/** + * prctl_set_seccomp: configures current->seccomp.mode + * @seccomp_mode: requested mode to use + * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER + * + * Returns 0 on success or -EINVAL on failure. + */ +long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter) +{ + unsigned int op; + void __user *uargs; switch (seccomp_mode) { case SECCOMP_MODE_STRICT: - ret = 0; -#ifdef TIF_NOTSC - disable_TSC(); -#endif + op = SECCOMP_SET_MODE_STRICT; + /* + * Setting strict mode through prctl always ignored filter, + * so make sure it is always NULL here to pass the internal + * check in do_seccomp(). + */ + uargs = NULL; break; -#ifdef CONFIG_SECCOMP_FILTER case SECCOMP_MODE_FILTER: - ret = seccomp_attach_user_filter(filter); - if (ret) - goto out; + op = SECCOMP_SET_MODE_FILTER; + uargs = filter; break; -#endif default: + return -EINVAL; + } + + /* prctl interface doesn't have flags, so they are always zero. */ + return do_seccomp(op, 0, uargs); +} + +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) +static struct seccomp_filter *get_nth_filter(struct task_struct *task, + unsigned long filter_off) +{ + struct seccomp_filter *orig, *filter; + unsigned long count; + + /* + * Note: this is only correct because the caller should be the (ptrace) + * tracer of the task, otherwise lock_task_sighand is needed. + */ + spin_lock_irq(&task->sighand->siglock); + + if (task->seccomp.mode != SECCOMP_MODE_FILTER) { + spin_unlock_irq(&task->sighand->siglock); + return ERR_PTR(-EINVAL); + } + + orig = task->seccomp.filter; + __get_seccomp_filter(orig); + spin_unlock_irq(&task->sighand->siglock); + + count = 0; + for (filter = orig; filter; filter = filter->prev) + count++; + + if (filter_off >= count) { + filter = ERR_PTR(-ENOENT); + goto out; + } + + count -= filter_off; + for (filter = orig; filter && count > 1; filter = filter->prev) + count--; + + if (WARN_ON(count != 1 || !filter)) { + filter = ERR_PTR(-ENOENT); + goto out; + } + + __get_seccomp_filter(filter); + +out: + __put_seccomp_filter(orig); + return filter; +} + +long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, + void __user *data) +{ + struct seccomp_filter *filter; + struct sock_fprog_kern *fprog; + long ret; + + if (!capable(CAP_SYS_ADMIN) || + current->seccomp.mode != SECCOMP_MODE_DISABLED) { + return -EACCES; + } + + filter = get_nth_filter(task, filter_off); + if (IS_ERR(filter)) + return PTR_ERR(filter); + + fprog = filter->prog->orig_prog; + if (!fprog) { + /* This must be a new non-cBPF filter, since we save + * every cBPF filter's orig_prog above when + * CONFIG_CHECKPOINT_RESTORE is enabled. + */ + ret = -EMEDIUMTYPE; goto out; } - current->seccomp.mode = seccomp_mode; - set_thread_flag(TIF_SECCOMP); + ret = fprog->len; + if (!data) + goto out; + + if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) + ret = -EFAULT; + out: + __put_seccomp_filter(filter); + return ret; +} + +long seccomp_get_metadata(struct task_struct *task, + unsigned long size, void __user *data) +{ + long ret; + struct seccomp_filter *filter; + struct seccomp_metadata kmd = {}; + + if (!capable(CAP_SYS_ADMIN) || + current->seccomp.mode != SECCOMP_MODE_DISABLED) { + return -EACCES; + } + + size = min_t(unsigned long, size, sizeof(kmd)); + + if (size < sizeof(kmd.filter_off)) + return -EINVAL; + + if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) + return -EFAULT; + + filter = get_nth_filter(task, kmd.filter_off); + if (IS_ERR(filter)) + return PTR_ERR(filter); + + if (filter->log) + kmd.flags |= SECCOMP_FILTER_FLAG_LOG; + + ret = size; + if (copy_to_user(data, &kmd, size)) + ret = -EFAULT; + + __put_seccomp_filter(filter); return ret; } +#endif + +#ifdef CONFIG_SYSCTL + +/* Human readable action names for friendly sysctl interaction */ +#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" +#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" +#define SECCOMP_RET_TRAP_NAME "trap" +#define SECCOMP_RET_ERRNO_NAME "errno" +#define SECCOMP_RET_USER_NOTIF_NAME "user_notif" +#define SECCOMP_RET_TRACE_NAME "trace" +#define SECCOMP_RET_LOG_NAME "log" +#define SECCOMP_RET_ALLOW_NAME "allow" + +static const char seccomp_actions_avail[] = + SECCOMP_RET_KILL_PROCESS_NAME " " + SECCOMP_RET_KILL_THREAD_NAME " " + SECCOMP_RET_TRAP_NAME " " + SECCOMP_RET_ERRNO_NAME " " + SECCOMP_RET_USER_NOTIF_NAME " " + SECCOMP_RET_TRACE_NAME " " + SECCOMP_RET_LOG_NAME " " + SECCOMP_RET_ALLOW_NAME; + +struct seccomp_log_name { + u32 log; + const char *name; +}; + +static const struct seccomp_log_name seccomp_log_names[] = { + { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, + { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, + { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, + { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, + { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME }, + { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, + { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, + { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, + { } +}; + +static bool seccomp_names_from_actions_logged(char *names, size_t size, + u32 actions_logged, + const char *sep) +{ + const struct seccomp_log_name *cur; + bool append_sep = false; + + for (cur = seccomp_log_names; cur->name && size; cur++) { + ssize_t ret; + + if (!(actions_logged & cur->log)) + continue; + + if (append_sep) { + ret = strscpy(names, sep, size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } else + append_sep = true; + + ret = strscpy(names, cur->name, size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } + + return true; +} + +static bool seccomp_action_logged_from_name(u32 *action_logged, + const char *name) +{ + const struct seccomp_log_name *cur; + + for (cur = seccomp_log_names; cur->name; cur++) { + if (!strcmp(cur->name, name)) { + *action_logged = cur->log; + return true; + } + } + + return false; +} + +static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) +{ + char *name; + + *actions_logged = 0; + while ((name = strsep(&names, " ")) && *name) { + u32 action_logged = 0; + + if (!seccomp_action_logged_from_name(&action_logged, name)) + return false; + + *actions_logged |= action_logged; + } + + return true; +} + +static int read_actions_logged(const struct ctl_table *ro_table, void *buffer, + size_t *lenp, loff_t *ppos) +{ + char names[sizeof(seccomp_actions_avail)]; + struct ctl_table table; + + memset(names, 0, sizeof(names)); + + if (!seccomp_names_from_actions_logged(names, sizeof(names), + seccomp_actions_logged, " ")) + return -EINVAL; + + table = *ro_table; + table.data = names; + table.maxlen = sizeof(names); + return proc_dostring(&table, 0, buffer, lenp, ppos); +} + +static int write_actions_logged(const struct ctl_table *ro_table, void *buffer, + size_t *lenp, loff_t *ppos, u32 *actions_logged) +{ + char names[sizeof(seccomp_actions_avail)]; + struct ctl_table table; + int ret; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + memset(names, 0, sizeof(names)); + + table = *ro_table; + table.data = names; + table.maxlen = sizeof(names); + ret = proc_dostring(&table, 1, buffer, lenp, ppos); + if (ret) + return ret; + + if (!seccomp_actions_logged_from_names(actions_logged, table.data)) + return -EINVAL; + + if (*actions_logged & SECCOMP_LOG_ALLOW) + return -EINVAL; + + seccomp_actions_logged = *actions_logged; + return 0; +} + +static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, + int ret) +{ + char names[sizeof(seccomp_actions_avail)]; + char old_names[sizeof(seccomp_actions_avail)]; + const char *new = names; + const char *old = old_names; + + if (!audit_enabled) + return; + + memset(names, 0, sizeof(names)); + memset(old_names, 0, sizeof(old_names)); + + if (ret) + new = "?"; + else if (!actions_logged) + new = "(none)"; + else if (!seccomp_names_from_actions_logged(names, sizeof(names), + actions_logged, ",")) + new = "?"; + + if (!old_actions_logged) + old = "(none)"; + else if (!seccomp_names_from_actions_logged(old_names, + sizeof(old_names), + old_actions_logged, ",")) + old = "?"; + + return audit_seccomp_actions_logged(new, old, !ret); +} + +static int seccomp_actions_logged_handler(const struct ctl_table *ro_table, int write, + void *buffer, size_t *lenp, + loff_t *ppos) +{ + int ret; + + if (write) { + u32 actions_logged = 0; + u32 old_actions_logged = seccomp_actions_logged; + + ret = write_actions_logged(ro_table, buffer, lenp, ppos, + &actions_logged); + audit_actions_logged(actions_logged, old_actions_logged, ret); + } else + ret = read_actions_logged(ro_table, buffer, lenp, ppos); + + return ret; +} + +static const struct ctl_table seccomp_sysctl_table[] = { + { + .procname = "actions_avail", + .data = (void *) &seccomp_actions_avail, + .maxlen = sizeof(seccomp_actions_avail), + .mode = 0444, + .proc_handler = proc_dostring, + }, + { + .procname = "actions_logged", + .mode = 0644, + .proc_handler = seccomp_actions_logged_handler, + }, +}; + +static int __init seccomp_sysctl_init(void) +{ + register_sysctl_init("kernel/seccomp", seccomp_sysctl_table); + return 0; +} + +device_initcall(seccomp_sysctl_init) + +#endif /* CONFIG_SYSCTL */ + +#ifdef CONFIG_SECCOMP_CACHE_DEBUG +/* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */ +static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name, + const void *bitmap, size_t bitmap_size) +{ + int nr; + + for (nr = 0; nr < bitmap_size; nr++) { + bool cached = test_bit(nr, bitmap); + char *status = cached ? "ALLOW" : "FILTER"; + + seq_printf(m, "%s %d %s\n", name, nr, status); + } +} + +int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task) +{ + struct seccomp_filter *f; + unsigned long flags; + + /* + * We don't want some sandboxed process to know what their seccomp + * filters consist of. + */ + if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN)) + return -EACCES; + + if (!lock_task_sighand(task, &flags)) + return -ESRCH; + + f = READ_ONCE(task->seccomp.filter); + if (!f) { + unlock_task_sighand(task, &flags); + return 0; + } + + /* prevent filter from being freed while we are printing it */ + __get_seccomp_filter(f); + unlock_task_sighand(task, &flags); + + proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME, + f->cache.allow_native, + SECCOMP_ARCH_NATIVE_NR); + +#ifdef SECCOMP_ARCH_COMPAT + proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME, + f->cache.allow_compat, + SECCOMP_ARCH_COMPAT_NR); +#endif /* SECCOMP_ARCH_COMPAT */ + + __put_seccomp_filter(f); + return 0; +} +#endif /* CONFIG_SECCOMP_CACHE_DEBUG */ |