diff options
Diffstat (limited to 'security/landlock/fs.c')
| -rw-r--r-- | security/landlock/fs.c | 104 |
1 files changed, 99 insertions, 5 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 87fde50eb550..adcea0fe7e68 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -146,7 +146,8 @@ retry: #define ACCESS_FILE ( \ LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ - LANDLOCK_ACCESS_FS_READ_FILE) + LANDLOCK_ACCESS_FS_READ_FILE | \ + LANDLOCK_ACCESS_FS_TRUNCATE) /* clang-format on */ /* @@ -1154,9 +1155,23 @@ static int hook_path_rmdir(const struct path *const dir, return current_check_access_path(dir, LANDLOCK_ACCESS_FS_REMOVE_DIR); } +static int hook_path_truncate(const struct path *const path) +{ + return current_check_access_path(path, LANDLOCK_ACCESS_FS_TRUNCATE); +} + /* File hooks */ -static inline access_mask_t get_file_access(const struct file *const file) +/** + * get_required_file_open_access - Get access needed to open a file + * + * @file: File being opened. + * + * Returns the access rights that are required for opening the given file, + * depending on the file type and open mode. + */ +static inline access_mask_t +get_required_file_open_access(const struct file *const file) { access_mask_t access = 0; @@ -1174,19 +1189,95 @@ static inline access_mask_t get_file_access(const struct file *const file) return access; } +static int hook_file_alloc_security(struct file *const file) +{ + /* + * Grants all access rights, even if most of them are not checked later + * on. It is more consistent. + * + * Notably, file descriptors for regular files can also be acquired + * without going through the file_open hook, for example when using + * memfd_create(2). + */ + landlock_file(file)->allowed_access = LANDLOCK_MASK_ACCESS_FS; + return 0; +} + static int hook_file_open(struct file *const file) { + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {}; + access_mask_t open_access_request, full_access_request, allowed_access; + const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE; const struct landlock_ruleset *const dom = landlock_get_current_domain(); if (!dom) return 0; + /* - * Because a file may be opened with O_PATH, get_file_access() may - * return 0. This case will be handled with a future Landlock + * Because a file may be opened with O_PATH, get_required_file_open_access() + * may return 0. This case will be handled with a future Landlock * evolution. */ - return check_access_path(dom, &file->f_path, get_file_access(file)); + open_access_request = get_required_file_open_access(file); + + /* + * We look up more access than what we immediately need for open(), so + * that we can later authorize operations on opened files. + */ + full_access_request = open_access_request | optional_access; + + if (is_access_to_paths_allowed( + dom, &file->f_path, + init_layer_masks(dom, full_access_request, &layer_masks), + &layer_masks, NULL, 0, NULL, NULL)) { + allowed_access = full_access_request; + } else { + unsigned long access_bit; + const unsigned long access_req = full_access_request; + + /* + * Calculate the actual allowed access rights from layer_masks. + * Add each access right to allowed_access which has not been + * vetoed by any layer. + */ + allowed_access = 0; + for_each_set_bit(access_bit, &access_req, + ARRAY_SIZE(layer_masks)) { + if (!layer_masks[access_bit]) + allowed_access |= BIT_ULL(access_bit); + } + } + + /* + * For operations on already opened files (i.e. ftruncate()), it is the + * access rights at the time of open() which decide whether the + * operation is permitted. Therefore, we record the relevant subset of + * file access rights in the opened struct file. + */ + landlock_file(file)->allowed_access = allowed_access; + + if ((open_access_request & allowed_access) == open_access_request) + return 0; + + return -EACCES; +} + +static int hook_file_truncate(struct file *const file) +{ + /* + * Allows truncation if the truncate right was available at the time of + * opening the file, to get a consistent access check as for read, write + * and execute operations. + * + * Note: For checks done based on the file's Landlock allowed access, we + * enforce them independently of whether the current thread is in a + * Landlock domain, so that open files passed between independent + * processes retain their behaviour. + */ + if (landlock_file(file)->allowed_access & LANDLOCK_ACCESS_FS_TRUNCATE) + return 0; + return -EACCES; } static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { @@ -1206,8 +1297,11 @@ static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(path_symlink, hook_path_symlink), 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(file_alloc_security, hook_file_alloc_security), LSM_HOOK_INIT(file_open, hook_file_open), + LSM_HOOK_INIT(file_truncate, hook_file_truncate), }; __init void landlock_add_fs_hooks(void) |