Add two flags LANDLOCK_ACCESS_FS_CHMOD and LANDLOCK_ACCESS_FS_CHGRP to support restriction to chmod(2) and chown(2) with landlock.
If these two access rights are set on a directory, they only take effect for its context, not the directory itself.
This patch also change the landlock ABI version from 3 to 4.
Signed-off-by: Xiu Jianfeng xiujianfeng@huawei.com --- include/uapi/linux/landlock.h | 10 +++-- security/landlock/fs.c | 43 +++++++++++++++++++- security/landlock/limits.h | 2 +- security/landlock/syscalls.c | 2 +- tools/testing/selftests/landlock/base_test.c | 2 +- tools/testing/selftests/landlock/fs_test.c | 6 ++- 6 files changed, 56 insertions(+), 9 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 735b1fe8326e..07b73626ff20 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -141,14 +141,16 @@ struct landlock_path_beneath_attr { * directory) parent. Otherwise, such actions are denied with errno set to * EACCES. The EACCES errno prevails over EXDEV to let user space * efficiently deal with an unrecoverable error. + * - %LANDLOCK_ACCESS_FS_CHMOD: Change the file mode bits of a file. + * - %LANDLOCK_ACCESS_FS_CHGRP: Change the owner and/or group of a file. * * .. warning:: * * It is currently not possible to restrict some file-related actions * accessible through these syscall families: :manpage:`chdir(2)`, - * :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`chmod(2)`, - * :manpage:`chown(2)`, :manpage:`setxattr(2)`, :manpage:`utime(2)`, - * :manpage:`ioctl(2)`, :manpage:`fcntl(2)`, :manpage:`access(2)`. + * :manpage:`stat(2)`, :manpage:`flock(2)`, :manpage:`setxattr(2)`, + * :manpage:`utime(2)`,:manpage:`ioctl(2)`, :manpage:`fcntl(2)`, + * :manpage:`access(2)`. * Future Landlock evolutions will enable to restrict them. */ /* clang-format off */ @@ -167,6 +169,8 @@ struct landlock_path_beneath_attr { #define LANDLOCK_ACCESS_FS_MAKE_SYM (1ULL << 12) #define LANDLOCK_ACCESS_FS_REFER (1ULL << 13) #define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14) +#define LANDLOCK_ACCESS_FS_CHMOD (1ULL << 15) +#define LANDLOCK_ACCESS_FS_CHGRP (1ULL << 16) /* clang-format on */
#endif /* _UAPI_LINUX_LANDLOCK_H */ diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 4ef614a4ea22..6ac83d96ada7 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -185,7 +185,9 @@ static struct landlock_object *get_inode_object(struct inode *const inode) LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ LANDLOCK_ACCESS_FS_READ_FILE | \ - LANDLOCK_ACCESS_FS_TRUNCATE) + LANDLOCK_ACCESS_FS_TRUNCATE | \ + LANDLOCK_ACCESS_FS_CHMOD | \ + LANDLOCK_ACCESS_FS_CHGRP) /* clang-format on */
/* @@ -690,6 +692,31 @@ static inline int current_check_access_path(const struct path *const path, return check_access_path(dom, path, access_request); }
+static inline int +current_check_access_path_context_only(const struct path *const path, + const access_mask_t access_request) +{ + const struct landlock_ruleset *const dom = + landlock_get_current_domain(); + struct path eff_path; + int ret; + + if (!dom) + return 0; + eff_path = *path; + /* if it's dir, check its visible parent. */ + if (d_is_dir(eff_path.dentry)) { + path_get(&eff_path); + /* dont care if reaches the root or not. */ + walk_to_visible_parent(&eff_path); + ret = current_check_access_path(&eff_path, access_request); + path_put(&eff_path); + } else { + ret = current_check_access_path(&eff_path, access_request); + } + return ret; +} + static inline access_mask_t get_mode_access(const umode_t mode) { switch (mode & S_IFMT) { @@ -1177,6 +1204,18 @@ static int hook_path_truncate(const struct path *const path) return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE); }
+static int hook_path_chmod(const struct path *const path, umode_t mode) +{ + return current_check_access_path_context_only(path, + LANDLOCK_ACCESS_FS_CHMOD); +} + +static int hook_path_chown(const struct path *const path, kuid_t uid, kgid_t gid) +{ + return current_check_access_path_context_only(path, + LANDLOCK_ACCESS_FS_CHGRP); +} + /* File hooks */
static inline access_mask_t get_file_access(const struct file *const file) @@ -1230,6 +1269,8 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(path_unlink, hook_path_unlink), LSM_HOOK_INIT(path_rmdir, hook_path_rmdir), LSM_HOOK_INIT(path_truncate, hook_path_truncate), + LSM_HOOK_INIT(path_chmod, hook_path_chmod), + LSM_HOOK_INIT(path_chown, hook_path_chown),
LSM_HOOK_INIT(file_open, hook_file_open), }; diff --git a/security/landlock/limits.h b/security/landlock/limits.h index 82288f0e9e5e..7cdd7d467d12 100644 --- a/security/landlock/limits.h +++ b/security/landlock/limits.h @@ -18,7 +18,7 @@ #define LANDLOCK_MAX_NUM_LAYERS 16 #define LANDLOCK_MAX_NUM_RULES U32_MAX
-#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_TRUNCATE +#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_CHGRP #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) #define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index f4d6fc7ed17f..469e0e11735c 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -129,7 +129,7 @@ static const struct file_operations ruleset_fops = { .write = fop_dummy_write, };
-#define LANDLOCK_ABI_VERSION 3 +#define LANDLOCK_ABI_VERSION 4
/** * sys_landlock_create_ruleset - Create a new ruleset diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c index 72cdae277b02..9f00582f639c 100644 --- a/tools/testing/selftests/landlock/base_test.c +++ b/tools/testing/selftests/landlock/base_test.c @@ -75,7 +75,7 @@ TEST(abi_version) const struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE, }; - ASSERT_EQ(3, landlock_create_ruleset(NULL, 0, + ASSERT_EQ(4, landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0, diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index debe2d9ea6cf..f513cd8d9d51 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -404,9 +404,11 @@ TEST_F_FORK(layout1, inval) LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ LANDLOCK_ACCESS_FS_READ_FILE | \ - LANDLOCK_ACCESS_FS_TRUNCATE) + LANDLOCK_ACCESS_FS_TRUNCATE | \ + LANDLOCK_ACCESS_FS_CHMOD | \ + LANDLOCK_ACCESS_FS_CHGRP)
-#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE +#define ACCESS_LAST LANDLOCK_ACCESS_FS_CHGRP
#define ACCESS_ALL ( \ ACCESS_FILE | \