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-rw-r--r--security/landlock/syscalls.c378
1 files changed, 246 insertions, 132 deletions
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 245cc650a4dc..0116e9f93ffe 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -1,15 +1,18 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
- * Landlock LSM - System call implementations and user space interfaces
+ * Landlock - System call implementations and user space interfaces
*
* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
+ * Copyright © 2021-2025 Microsoft Corporation
*/
#include <asm/current.h>
#include <linux/anon_inodes.h>
+#include <linux/bitops.h>
#include <linux/build_bug.h>
#include <linux/capability.h>
+#include <linux/cleanup.h>
#include <linux/compiler_types.h>
#include <linux/dcache.h>
#include <linux/err.h>
@@ -27,11 +30,25 @@
#include <uapi/linux/landlock.h>
#include "cred.h"
+#include "domain.h"
#include "fs.h"
#include "limits.h"
+#include "net.h"
#include "ruleset.h"
#include "setup.h"
+static bool is_initialized(void)
+{
+ if (likely(landlock_initialized))
+ return true;
+
+ pr_warn_once(
+ "Disabled but requested by user space. "
+ "You should enable Landlock at boot time: "
+ "https://docs.kernel.org/userspace-api/landlock.html#boot-time-configuration\n");
+ return false;
+}
+
/**
* copy_min_struct_from_user - Safe future-proof argument copying
*
@@ -74,7 +91,8 @@ static void build_check_abi(void)
{
struct landlock_ruleset_attr ruleset_attr;
struct landlock_path_beneath_attr path_beneath_attr;
- size_t ruleset_size, path_beneath_size;
+ struct landlock_net_port_attr net_port_attr;
+ size_t ruleset_size, path_beneath_size, net_port_size;
/*
* For each user space ABI structures, first checks that there is no
@@ -82,13 +100,20 @@ static void build_check_abi(void)
* struct size.
*/
ruleset_size = sizeof(ruleset_attr.handled_access_fs);
+ ruleset_size += sizeof(ruleset_attr.handled_access_net);
+ ruleset_size += sizeof(ruleset_attr.scoped);
BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
- BUILD_BUG_ON(sizeof(ruleset_attr) != 8);
+ BUILD_BUG_ON(sizeof(ruleset_attr) != 24);
path_beneath_size = sizeof(path_beneath_attr.allowed_access);
path_beneath_size += sizeof(path_beneath_attr.parent_fd);
BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size);
BUILD_BUG_ON(sizeof(path_beneath_attr) != 12);
+
+ net_port_size = sizeof(net_port_attr.allowed_access);
+ net_port_size += sizeof(net_port_attr.port);
+ BUILD_BUG_ON(sizeof(net_port_attr) != net_port_size);
+ BUILD_BUG_ON(sizeof(net_port_attr) != 16);
}
/* Ruleset handling */
@@ -129,7 +154,14 @@ static const struct file_operations ruleset_fops = {
.write = fop_dummy_write,
};
-#define LANDLOCK_ABI_VERSION 3
+/*
+ * The Landlock ABI version should be incremented for each new Landlock-related
+ * user space visible change (e.g. Landlock syscalls). This version should
+ * only be incremented once per Linux release, and the date in
+ * Documentation/userspace-api/landlock.rst should be updated to reflect the
+ * UAPI change.
+ */
+const int landlock_abi_version = 7;
/**
* sys_landlock_create_ruleset - Create a new ruleset
@@ -138,21 +170,27 @@ static const struct file_operations ruleset_fops = {
* the new ruleset.
* @size: Size of the pointed &struct landlock_ruleset_attr (needed for
* backward and forward compatibility).
- * @flags: Supported value: %LANDLOCK_CREATE_RULESET_VERSION.
+ * @flags: Supported values:
+ *
+ * - %LANDLOCK_CREATE_RULESET_VERSION
+ * - %LANDLOCK_CREATE_RULESET_ERRATA
*
* This system call enables to create a new Landlock ruleset, and returns the
* related file descriptor on success.
*
- * If @flags is %LANDLOCK_CREATE_RULESET_VERSION and @attr is NULL and @size is
- * 0, then the returned value is the highest supported Landlock ABI version
- * (starting at 1).
+ * If %LANDLOCK_CREATE_RULESET_VERSION or %LANDLOCK_CREATE_RULESET_ERRATA is
+ * set, then @attr must be NULL and @size must be 0.
*
* Possible returned errors are:
*
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
- * - %EINVAL: unknown @flags, or unknown access, or too small @size;
- * - %E2BIG or %EFAULT: @attr or @size inconsistencies;
+ * - %EINVAL: unknown @flags, or unknown access, or unknown scope, or too small @size;
+ * - %E2BIG: @attr or @size inconsistencies;
+ * - %EFAULT: @attr or @size inconsistencies;
* - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs.
+ *
+ * .. kernel-doc:: include/uapi/linux/landlock.h
+ * :identifiers: landlock_create_ruleset_flags
*/
SYSCALL_DEFINE3(landlock_create_ruleset,
const struct landlock_ruleset_attr __user *const, attr,
@@ -165,13 +203,19 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
/* Build-time checks. */
build_check_abi();
- if (!landlock_initialized)
+ if (!is_initialized())
return -EOPNOTSUPP;
if (flags) {
- if ((flags == LANDLOCK_CREATE_RULESET_VERSION) && !attr &&
- !size)
- return LANDLOCK_ABI_VERSION;
+ if (attr || size)
+ return -EINVAL;
+
+ if (flags == LANDLOCK_CREATE_RULESET_VERSION)
+ return landlock_abi_version;
+
+ if (flags == LANDLOCK_CREATE_RULESET_ERRATA)
+ return landlock_errata;
+
return -EINVAL;
}
@@ -188,8 +232,19 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
LANDLOCK_MASK_ACCESS_FS)
return -EINVAL;
+ /* Checks network content (and 32-bits cast). */
+ if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
+ LANDLOCK_MASK_ACCESS_NET)
+ return -EINVAL;
+
+ /* Checks IPC scoping content (and 32-bits cast). */
+ if ((ruleset_attr.scoped | LANDLOCK_MASK_SCOPE) != LANDLOCK_MASK_SCOPE)
+ return -EINVAL;
+
/* Checks arguments and transforms to kernel struct. */
- ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+ ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
+ ruleset_attr.handled_access_net,
+ ruleset_attr.scoped);
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
@@ -208,31 +263,21 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
static struct landlock_ruleset *get_ruleset_from_fd(const int fd,
const fmode_t mode)
{
- struct fd ruleset_f;
+ CLASS(fd, ruleset_f)(fd);
struct landlock_ruleset *ruleset;
- ruleset_f = fdget(fd);
- if (!ruleset_f.file)
+ if (fd_empty(ruleset_f))
return ERR_PTR(-EBADF);
/* Checks FD type and access right. */
- if (ruleset_f.file->f_op != &ruleset_fops) {
- ruleset = ERR_PTR(-EBADFD);
- goto out_fdput;
- }
- if (!(ruleset_f.file->f_mode & mode)) {
- ruleset = ERR_PTR(-EPERM);
- goto out_fdput;
- }
- ruleset = ruleset_f.file->private_data;
- if (WARN_ON_ONCE(ruleset->num_layers != 1)) {
- ruleset = ERR_PTR(-EINVAL);
- goto out_fdput;
- }
+ if (fd_file(ruleset_f)->f_op != &ruleset_fops)
+ return ERR_PTR(-EBADFD);
+ if (!(fd_file(ruleset_f)->f_mode & mode))
+ return ERR_PTR(-EPERM);
+ ruleset = fd_file(ruleset_f)->private_data;
+ if (WARN_ON_ONCE(ruleset->num_layers != 1))
+ return ERR_PTR(-EINVAL);
landlock_get_ruleset(ruleset);
-
-out_fdput:
- fdput(ruleset_f);
return ruleset;
}
@@ -243,46 +288,108 @@ out_fdput:
*/
static int get_path_from_fd(const s32 fd, struct path *const path)
{
- struct fd f;
- int err = 0;
+ CLASS(fd_raw, f)(fd);
BUILD_BUG_ON(!__same_type(
fd, ((struct landlock_path_beneath_attr *)NULL)->parent_fd));
- /* Handles O_PATH. */
- f = fdget_raw(fd);
- if (!f.file)
+ if (fd_empty(f))
return -EBADF;
/*
* Forbids ruleset FDs, internal filesystems (e.g. nsfs), including
* pseudo filesystems that will never be mountable (e.g. sockfs,
* pipefs).
*/
- if ((f.file->f_op == &ruleset_fops) ||
- (f.file->f_path.mnt->mnt_flags & MNT_INTERNAL) ||
- (f.file->f_path.dentry->d_sb->s_flags & SB_NOUSER) ||
- d_is_negative(f.file->f_path.dentry) ||
- IS_PRIVATE(d_backing_inode(f.file->f_path.dentry))) {
- err = -EBADFD;
- goto out_fdput;
- }
- *path = f.file->f_path;
+ if ((fd_file(f)->f_op == &ruleset_fops) ||
+ (fd_file(f)->f_path.mnt->mnt_flags & MNT_INTERNAL) ||
+ (fd_file(f)->f_path.dentry->d_sb->s_flags & SB_NOUSER) ||
+ IS_PRIVATE(d_backing_inode(fd_file(f)->f_path.dentry)))
+ return -EBADFD;
+
+ *path = fd_file(f)->f_path;
path_get(path);
+ return 0;
+}
+
+static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
+ const void __user *const rule_attr)
+{
+ struct landlock_path_beneath_attr path_beneath_attr;
+ struct path path;
+ int res, err;
+ access_mask_t mask;
+
+ /* Copies raw user space buffer. */
+ res = copy_from_user(&path_beneath_attr, rule_attr,
+ sizeof(path_beneath_attr));
+ if (res)
+ return -EFAULT;
+
+ /*
+ * Informs about useless rule: empty allowed_access (i.e. deny rules)
+ * are ignored in path walks.
+ */
+ if (!path_beneath_attr.allowed_access)
+ return -ENOMSG;
+
+ /* Checks that allowed_access matches the @ruleset constraints. */
+ mask = ruleset->access_masks[0].fs;
+ if ((path_beneath_attr.allowed_access | mask) != mask)
+ return -EINVAL;
+
+ /* Gets and checks the new rule. */
+ err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
+ if (err)
+ return err;
-out_fdput:
- fdput(f);
+ /* Imports the new rule. */
+ err = landlock_append_fs_rule(ruleset, &path,
+ path_beneath_attr.allowed_access);
+ path_put(&path);
return err;
}
+static int add_rule_net_port(struct landlock_ruleset *ruleset,
+ const void __user *const rule_attr)
+{
+ struct landlock_net_port_attr net_port_attr;
+ int res;
+ access_mask_t mask;
+
+ /* Copies raw user space buffer. */
+ res = copy_from_user(&net_port_attr, rule_attr, sizeof(net_port_attr));
+ if (res)
+ return -EFAULT;
+
+ /*
+ * Informs about useless rule: empty allowed_access (i.e. deny rules)
+ * are ignored by network actions.
+ */
+ if (!net_port_attr.allowed_access)
+ return -ENOMSG;
+
+ /* Checks that allowed_access matches the @ruleset constraints. */
+ mask = landlock_get_net_access_mask(ruleset, 0);
+ if ((net_port_attr.allowed_access | mask) != mask)
+ return -EINVAL;
+
+ /* Denies inserting a rule with port greater than 65535. */
+ if (net_port_attr.port > U16_MAX)
+ return -EINVAL;
+
+ /* Imports the new rule. */
+ return landlock_append_net_rule(ruleset, net_port_attr.port,
+ net_port_attr.allowed_access);
+}
+
/**
* sys_landlock_add_rule - Add a new rule to a ruleset
*
* @ruleset_fd: File descriptor tied to the ruleset that should be extended
* with the new rule.
- * @rule_type: Identify the structure type pointed to by @rule_attr (only
- * %LANDLOCK_RULE_PATH_BENEATH for now).
- * @rule_attr: Pointer to a rule (only of type &struct
- * landlock_path_beneath_attr for now).
+ * @rule_type: Identify the structure type pointed to by @rule_attr:
+ * %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_PORT.
+ * @rule_attr: Pointer to a rule (matching the @rule_type).
* @flags: Must be 0.
*
* This system call enables to define a new rule and add it to an existing
@@ -291,27 +398,30 @@ out_fdput:
* Possible returned errors are:
*
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
- * - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
- * &landlock_path_beneath_attr.allowed_access is not a subset of the
- * ruleset handled accesses);
- * - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
+ * - %EAFNOSUPPORT: @rule_type is %LANDLOCK_RULE_NET_PORT but TCP/IP is not
+ * supported by the running kernel;
+ * - %EINVAL: @flags is not 0;
+ * - %EINVAL: The rule accesses are inconsistent (i.e.
+ * &landlock_path_beneath_attr.allowed_access or
+ * &landlock_net_port_attr.allowed_access is not a subset of the ruleset
+ * handled accesses)
+ * - %EINVAL: &landlock_net_port_attr.port is greater than 65535;
+ * - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access is
+ * 0);
* - %EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
* member of @rule_attr is not a file descriptor as expected;
* - %EBADFD: @ruleset_fd is not a ruleset file descriptor, or a member of
* @rule_attr is not the expected file descriptor type;
* - %EPERM: @ruleset_fd has no write access to the underlying ruleset;
- * - %EFAULT: @rule_attr inconsistency.
+ * - %EFAULT: @rule_attr was not a valid address.
*/
SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
const enum landlock_rule_type, rule_type,
const void __user *const, rule_attr, const __u32, flags)
{
- struct landlock_path_beneath_attr path_beneath_attr;
- struct path path;
- struct landlock_ruleset *ruleset;
- int res, err;
+ struct landlock_ruleset *ruleset __free(landlock_put_ruleset) = NULL;
- if (!landlock_initialized)
+ if (!is_initialized())
return -EOPNOTSUPP;
/* No flag for now. */
@@ -323,50 +433,14 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
- if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
- err = -EINVAL;
- goto out_put_ruleset;
- }
-
- /* Copies raw user space buffer, only one type for now. */
- res = copy_from_user(&path_beneath_attr, rule_attr,
- sizeof(path_beneath_attr));
- if (res) {
- err = -EFAULT;
- goto out_put_ruleset;
- }
-
- /*
- * Informs about useless rule: empty allowed_access (i.e. deny rules)
- * are ignored in path walks.
- */
- if (!path_beneath_attr.allowed_access) {
- err = -ENOMSG;
- goto out_put_ruleset;
- }
- /*
- * Checks that allowed_access matches the @ruleset constraints
- * (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
- */
- if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
- ruleset->fs_access_masks[0]) {
- err = -EINVAL;
- goto out_put_ruleset;
+ switch (rule_type) {
+ case LANDLOCK_RULE_PATH_BENEATH:
+ return add_rule_path_beneath(ruleset, rule_attr);
+ case LANDLOCK_RULE_NET_PORT:
+ return add_rule_net_port(ruleset, rule_attr);
+ default:
+ return -EINVAL;
}
-
- /* Gets and checks the new rule. */
- err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
- if (err)
- goto out_put_ruleset;
-
- /* Imports the new rule. */
- err = landlock_append_fs_rule(ruleset, &path,
- path_beneath_attr.allowed_access);
- path_put(&path);
-
-out_put_ruleset:
- landlock_put_ruleset(ruleset);
- return err;
}
/* Enforcement */
@@ -375,7 +449,11 @@ out_put_ruleset:
* sys_landlock_restrict_self - Enforce a ruleset on the calling thread
*
* @ruleset_fd: File descriptor tied to the ruleset to merge with the target.
- * @flags: Must be 0.
+ * @flags: Supported values:
+ *
+ * - %LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF
+ * - %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON
+ * - %LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF
*
* This system call enables to enforce a Landlock ruleset on the current
* thread. Enforcing a ruleset requires that the task has %CAP_SYS_ADMIN in its
@@ -385,7 +463,7 @@ out_put_ruleset:
* Possible returned errors are:
*
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
- * - %EINVAL: @flags is not 0.
+ * - %EINVAL: @flags contains an unknown bit.
* - %EBADF: @ruleset_fd is not a file descriptor for the current thread;
* - %EBADFD: @ruleset_fd is not a ruleset file descriptor;
* - %EPERM: @ruleset_fd has no read access to the underlying ruleset, or the
@@ -393,16 +471,21 @@ out_put_ruleset:
* %CAP_SYS_ADMIN in its namespace.
* - %E2BIG: The maximum number of stacked rulesets is reached for the current
* thread.
+ *
+ * .. kernel-doc:: include/uapi/linux/landlock.h
+ * :identifiers: landlock_restrict_self_flags
*/
SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
flags)
{
- struct landlock_ruleset *new_dom, *ruleset;
+ struct landlock_ruleset *new_dom,
+ *ruleset __free(landlock_put_ruleset) = NULL;
struct cred *new_cred;
struct landlock_cred_security *new_llcred;
- int err;
+ bool __maybe_unused log_same_exec, log_new_exec, log_subdomains,
+ prev_log_subdomains;
- if (!landlock_initialized)
+ if (!is_initialized())
return -EOPNOTSUPP;
/*
@@ -413,44 +496,75 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
return -EPERM;
- /* No flag for now. */
- if (flags)
+ if ((flags | LANDLOCK_MASK_RESTRICT_SELF) !=
+ LANDLOCK_MASK_RESTRICT_SELF)
return -EINVAL;
- /* Gets and checks the ruleset. */
- ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
- if (IS_ERR(ruleset))
- return PTR_ERR(ruleset);
+ /* Translates "off" flag to boolean. */
+ log_same_exec = !(flags & LANDLOCK_RESTRICT_SELF_LOG_SAME_EXEC_OFF);
+ /* Translates "on" flag to boolean. */
+ log_new_exec = !!(flags & LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON);
+ /* Translates "off" flag to boolean. */
+ log_subdomains = !(flags & LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF);
+
+ /*
+ * It is allowed to set LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF with
+ * -1 as ruleset_fd, but no other flag must be set.
+ */
+ if (!(ruleset_fd == -1 &&
+ flags == LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF)) {
+ /* Gets and checks the ruleset. */
+ ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
+ if (IS_ERR(ruleset))
+ return PTR_ERR(ruleset);
+ }
/* Prepares new credentials. */
new_cred = prepare_creds();
- if (!new_cred) {
- err = -ENOMEM;
- goto out_put_ruleset;
- }
+ if (!new_cred)
+ return -ENOMEM;
+
new_llcred = landlock_cred(new_cred);
+#ifdef CONFIG_AUDIT
+ prev_log_subdomains = !new_llcred->log_subdomains_off;
+ new_llcred->log_subdomains_off = !prev_log_subdomains ||
+ !log_subdomains;
+#endif /* CONFIG_AUDIT */
+
+ /*
+ * The only case when a ruleset may not be set is if
+ * LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF is set and ruleset_fd is -1.
+ * We could optimize this case by not calling commit_creds() if this flag
+ * was already set, but it is not worth the complexity.
+ */
+ if (!ruleset)
+ return commit_creds(new_cred);
+
/*
* There is no possible race condition while copying and manipulating
* the current credentials because they are dedicated per thread.
*/
new_dom = landlock_merge_ruleset(new_llcred->domain, ruleset);
if (IS_ERR(new_dom)) {
- err = PTR_ERR(new_dom);
- goto out_put_creds;
+ abort_creds(new_cred);
+ return PTR_ERR(new_dom);
}
+#ifdef CONFIG_AUDIT
+ new_dom->hierarchy->log_same_exec = log_same_exec;
+ new_dom->hierarchy->log_new_exec = log_new_exec;
+ if ((!log_same_exec && !log_new_exec) || !prev_log_subdomains)
+ new_dom->hierarchy->log_status = LANDLOCK_LOG_DISABLED;
+#endif /* CONFIG_AUDIT */
+
/* Replaces the old (prepared) domain. */
landlock_put_ruleset(new_llcred->domain);
new_llcred->domain = new_dom;
- landlock_put_ruleset(ruleset);
- return commit_creds(new_cred);
-
-out_put_creds:
- abort_creds(new_cred);
+#ifdef CONFIG_AUDIT
+ new_llcred->domain_exec |= BIT(new_dom->num_layers - 1);
+#endif /* CONFIG_AUDIT */
-out_put_ruleset:
- landlock_put_ruleset(ruleset);
- return err;
+ return commit_creds(new_cred);
}