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-rw-r--r--kernel/futex/syscalls.c398
1 files changed, 398 insertions, 0 deletions
diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
new file mode 100644
index 000000000000..6f91a07a6a83
--- /dev/null
+++ b/kernel/futex/syscalls.c
@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/compat.h>
+#include <linux/syscalls.h>
+#include <linux/time_namespace.h>
+
+#include "futex.h"
+
+/*
+ * Support for robust futexes: the kernel cleans up held futexes at
+ * thread exit time.
+ *
+ * Implementation: user-space maintains a per-thread list of locks it
+ * is holding. Upon do_exit(), the kernel carefully walks this list,
+ * and marks all locks that are owned by this thread with the
+ * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
+ * always manipulated with the lock held, so the list is private and
+ * per-thread. Userspace also maintains a per-thread 'list_op_pending'
+ * field, to allow the kernel to clean up if the thread dies after
+ * acquiring the lock, but just before it could have added itself to
+ * the list. There can only be one such pending lock.
+ */
+
+/**
+ * sys_set_robust_list() - Set the robust-futex list head of a task
+ * @head: pointer to the list-head
+ * @len: length of the list-head, as userspace expects
+ */
+SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
+ size_t, len)
+{
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+ /*
+ * The kernel knows only one size for now:
+ */
+ if (unlikely(len != sizeof(*head)))
+ return -EINVAL;
+
+ current->robust_list = head;
+
+ return 0;
+}
+
+/**
+ * sys_get_robust_list() - Get the robust-futex list head of a task
+ * @pid: pid of the process [zero for current task]
+ * @head_ptr: pointer to a list-head pointer, the kernel fills it in
+ * @len_ptr: pointer to a length field, the kernel fills in the header size
+ */
+SYSCALL_DEFINE3(get_robust_list, int, pid,
+ struct robust_list_head __user * __user *, head_ptr,
+ size_t __user *, len_ptr)
+{
+ struct robust_list_head __user *head;
+ unsigned long ret;
+ struct task_struct *p;
+
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+
+ rcu_read_lock();
+
+ ret = -ESRCH;
+ if (!pid)
+ p = current;
+ else {
+ p = find_task_by_vpid(pid);
+ if (!p)
+ goto err_unlock;
+ }
+
+ ret = -EPERM;
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
+ goto err_unlock;
+
+ head = p->robust_list;
+ rcu_read_unlock();
+
+ if (put_user(sizeof(*head), len_ptr))
+ return -EFAULT;
+ return put_user(head, head_ptr);
+
+err_unlock:
+ rcu_read_unlock();
+
+ return ret;
+}
+
+long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
+ u32 __user *uaddr2, u32 val2, u32 val3)
+{
+ int cmd = op & FUTEX_CMD_MASK;
+ unsigned int flags = 0;
+
+ if (!(op & FUTEX_PRIVATE_FLAG))
+ flags |= FLAGS_SHARED;
+
+ if (op & FUTEX_CLOCK_REALTIME) {
+ flags |= FLAGS_CLOCKRT;
+ if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
+ cmd != FUTEX_LOCK_PI2)
+ return -ENOSYS;
+ }
+
+ switch (cmd) {
+ case FUTEX_LOCK_PI:
+ case FUTEX_LOCK_PI2:
+ case FUTEX_UNLOCK_PI:
+ case FUTEX_TRYLOCK_PI:
+ case FUTEX_WAIT_REQUEUE_PI:
+ case FUTEX_CMP_REQUEUE_PI:
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+ }
+
+ switch (cmd) {
+ case FUTEX_WAIT:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ fallthrough;
+ case FUTEX_WAIT_BITSET:
+ return futex_wait(uaddr, flags, val, timeout, val3);
+ case FUTEX_WAKE:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ fallthrough;
+ case FUTEX_WAKE_BITSET:
+ return futex_wake(uaddr, flags, val, val3);
+ case FUTEX_REQUEUE:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
+ case FUTEX_CMP_REQUEUE:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
+ case FUTEX_WAKE_OP:
+ return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
+ case FUTEX_LOCK_PI:
+ flags |= FLAGS_CLOCKRT;
+ fallthrough;
+ case FUTEX_LOCK_PI2:
+ return futex_lock_pi(uaddr, flags, timeout, 0);
+ case FUTEX_UNLOCK_PI:
+ return futex_unlock_pi(uaddr, flags);
+ case FUTEX_TRYLOCK_PI:
+ return futex_lock_pi(uaddr, flags, NULL, 1);
+ case FUTEX_WAIT_REQUEUE_PI:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+ uaddr2);
+ case FUTEX_CMP_REQUEUE_PI:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
+ }
+ return -ENOSYS;
+}
+
+static __always_inline bool futex_cmd_has_timeout(u32 cmd)
+{
+ switch (cmd) {
+ case FUTEX_WAIT:
+ case FUTEX_LOCK_PI:
+ case FUTEX_LOCK_PI2:
+ case FUTEX_WAIT_BITSET:
+ case FUTEX_WAIT_REQUEUE_PI:
+ return true;
+ }
+ return false;
+}
+
+static __always_inline int
+futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
+{
+ if (!timespec64_valid(ts))
+ return -EINVAL;
+
+ *t = timespec64_to_ktime(*ts);
+ if (cmd == FUTEX_WAIT)
+ *t = ktime_add_safe(ktime_get(), *t);
+ else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
+ *t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
+ return 0;
+}
+
+SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
+ const struct __kernel_timespec __user *, utime,
+ u32 __user *, uaddr2, u32, val3)
+{
+ int ret, cmd = op & FUTEX_CMD_MASK;
+ ktime_t t, *tp = NULL;
+ struct timespec64 ts;
+
+ if (utime && futex_cmd_has_timeout(cmd)) {
+ if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
+ return -EFAULT;
+ if (get_timespec64(&ts, utime))
+ return -EFAULT;
+ ret = futex_init_timeout(cmd, op, &ts, &t);
+ if (ret)
+ return ret;
+ tp = &t;
+ }
+
+ return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
+}
+
+/* Mask of available flags for each futex in futex_waitv list */
+#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG)
+
+/**
+ * futex_parse_waitv - Parse a waitv array from userspace
+ * @futexv: Kernel side list of waiters to be filled
+ * @uwaitv: Userspace list to be parsed
+ * @nr_futexes: Length of futexv
+ *
+ * Return: Error code on failure, 0 on success
+ */
+static int futex_parse_waitv(struct futex_vector *futexv,
+ struct futex_waitv __user *uwaitv,
+ unsigned int nr_futexes)
+{
+ struct futex_waitv aux;
+ unsigned int i;
+
+ for (i = 0; i < nr_futexes; i++) {
+ if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
+ return -EFAULT;
+
+ if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved)
+ return -EINVAL;
+
+ if (!(aux.flags & FUTEX_32))
+ return -EINVAL;
+
+ futexv[i].w.flags = aux.flags;
+ futexv[i].w.val = aux.val;
+ futexv[i].w.uaddr = aux.uaddr;
+ futexv[i].q = futex_q_init;
+ }
+
+ return 0;
+}
+
+/**
+ * sys_futex_waitv - Wait on a list of futexes
+ * @waiters: List of futexes to wait on
+ * @nr_futexes: Length of futexv
+ * @flags: Flag for timeout (monotonic/realtime)
+ * @timeout: Optional absolute timeout.
+ * @clockid: Clock to be used for the timeout, realtime or monotonic.
+ *
+ * Given an array of `struct futex_waitv`, wait on each uaddr. The thread wakes
+ * if a futex_wake() is performed at any uaddr. The syscall returns immediately
+ * if any waiter has *uaddr != val. *timeout is an optional timeout value for
+ * the operation. Each waiter has individual flags. The `flags` argument for
+ * the syscall should be used solely for specifying the timeout as realtime, if
+ * needed. Flags for private futexes, sizes, etc. should be used on the
+ * individual flags of each waiter.
+ *
+ * Returns the array index of one of the woken futexes. No further information
+ * is provided: any number of other futexes may also have been woken by the
+ * same event, and if more than one futex was woken, the retrned index may
+ * refer to any one of them. (It is not necessaryily the futex with the
+ * smallest index, nor the one most recently woken, nor...)
+ */
+
+SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
+ unsigned int, nr_futexes, unsigned int, flags,
+ struct __kernel_timespec __user *, timeout, clockid_t, clockid)
+{
+ struct hrtimer_sleeper to;
+ struct futex_vector *futexv;
+ struct timespec64 ts;
+ ktime_t time;
+ int ret;
+
+ /* This syscall supports no flags for now */
+ if (flags)
+ return -EINVAL;
+
+ if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters)
+ return -EINVAL;
+
+ if (timeout) {
+ int flag_clkid = 0, flag_init = 0;
+
+ if (clockid == CLOCK_REALTIME) {
+ flag_clkid = FLAGS_CLOCKRT;
+ flag_init = FUTEX_CLOCK_REALTIME;
+ }
+
+ if (clockid != CLOCK_REALTIME && clockid != CLOCK_MONOTONIC)
+ return -EINVAL;
+
+ if (get_timespec64(&ts, timeout))
+ return -EFAULT;
+
+ /*
+ * Since there's no opcode for futex_waitv, use
+ * FUTEX_WAIT_BITSET that uses absolute timeout as well
+ */
+ ret = futex_init_timeout(FUTEX_WAIT_BITSET, flag_init, &ts, &time);
+ if (ret)
+ return ret;
+
+ futex_setup_timer(&time, &to, flag_clkid, 0);
+ }
+
+ futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
+ if (!futexv)
+ return -ENOMEM;
+
+ ret = futex_parse_waitv(futexv, waiters, nr_futexes);
+ if (!ret)
+ ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);
+
+ if (timeout) {
+ hrtimer_cancel(&to.timer);
+ destroy_hrtimer_on_stack(&to.timer);
+ }
+
+ kfree(futexv);
+ return ret;
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(set_robust_list,
+ struct compat_robust_list_head __user *, head,
+ compat_size_t, len)
+{
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+
+ if (unlikely(len != sizeof(*head)))
+ return -EINVAL;
+
+ current->compat_robust_list = head;
+
+ return 0;
+}
+
+COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
+ compat_uptr_t __user *, head_ptr,
+ compat_size_t __user *, len_ptr)
+{
+ struct compat_robust_list_head __user *head;
+ unsigned long ret;
+ struct task_struct *p;
+
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+
+ rcu_read_lock();
+
+ ret = -ESRCH;
+ if (!pid)
+ p = current;
+ else {
+ p = find_task_by_vpid(pid);
+ if (!p)
+ goto err_unlock;
+ }
+
+ ret = -EPERM;
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
+ goto err_unlock;
+
+ head = p->compat_robust_list;
+ rcu_read_unlock();
+
+ if (put_user(sizeof(*head), len_ptr))
+ return -EFAULT;
+ return put_user(ptr_to_compat(head), head_ptr);
+
+err_unlock:
+ rcu_read_unlock();
+
+ return ret;
+}
+#endif /* CONFIG_COMPAT */
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
+ const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
+ u32, val3)
+{
+ int ret, cmd = op & FUTEX_CMD_MASK;
+ ktime_t t, *tp = NULL;
+ struct timespec64 ts;
+
+ if (utime && futex_cmd_has_timeout(cmd)) {
+ if (get_old_timespec32(&ts, utime))
+ return -EFAULT;
+ ret = futex_init_timeout(cmd, op, &ts, &t);
+ if (ret)
+ return ret;
+ tp = &t;
+ }
+
+ return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
+}
+#endif /* CONFIG_COMPAT_32BIT_TIME */
+