From 42212936d9d811c7cf6efc4804747a6c417aafd4 Mon Sep 17 00:00:00 2001 From: Ivanov Mikhail Date: Tue, 26 Mar 2024 17:56:25 +0800 Subject: [PATCH 01/13] samples/landlock: Fix incorrect free in populate_ruleset_net MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Pointer env_port_name changes after strsep(). Memory allocated via strdup() will not be freed if landlock_add_rule() returns non-zero value. Fixes: 5e990dcef12e ("samples/landlock: Support TCP restrictions") Signed-off-by: Ivanov Mikhail Reviewed-by: Konstantin Meskhidze Link: https://lore.kernel.org/r/20240326095625.3576164-1-ivanov.mikhail1@huawei-partners.com Signed-off-by: Mickaël Salaün --- samples/landlock/sandboxer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 32e930c853bb..8b8ecd65c28c 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -153,7 +153,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, const __u64 allowed_access) { int ret = 1; - char *env_port_name, *strport; + char *env_port_name, *env_port_name_next, *strport; struct landlock_net_port_attr net_port = { .allowed_access = allowed_access, .port = 0, @@ -165,7 +165,8 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, env_port_name = strdup(env_port_name); unsetenv(env_var); - while ((strport = strsep(&env_port_name, ENV_DELIMITER))) { + env_port_name_next = env_port_name; + while ((strport = strsep(&env_port_name_next, ENV_DELIMITER))) { net_port.port = atoi(strport); if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT, &net_port, 0)) { From b25f7415eb4108aa32dd3e74289d7f997090708f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:12 +0000 Subject: [PATCH 02/13] landlock: Add IOCTL access right for character and block devices MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Introduces the LANDLOCK_ACCESS_FS_IOCTL_DEV right and increments the Landlock ABI version to 5. This access right applies to device-custom IOCTL commands when they are invoked on block or character device files. Like the truncate right, this right is associated with a file descriptor at the time of open(2), and gets respected even when the file descriptor is used outside of the thread which it was originally opened in. Therefore, a newly enabled Landlock policy does not apply to file descriptors which are already open. If the LANDLOCK_ACCESS_FS_IOCTL_DEV right is handled, only a small number of safe IOCTL commands will be permitted on newly opened device files. These include FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC, as well as other IOCTL commands for regular files which are implemented in fs/ioctl.c. Noteworthy scenarios which require special attention: TTY devices are often passed into a process from the parent process, and so a newly enabled Landlock policy does not retroactively apply to them automatically. In the past, TTY devices have often supported IOCTL commands like TIOCSTI and some TIOCLINUX subcommands, which were letting callers control the TTY input buffer (and simulate keypresses). This should be restricted to CAP_SYS_ADMIN programs on modern kernels though. Known limitations: The LANDLOCK_ACCESS_FS_IOCTL_DEV access right is a coarse-grained control over IOCTL commands. Landlock users may use path-based restrictions in combination with their knowledge about the file system layout to control what IOCTLs can be done. Cc: Paul Moore Cc: Christian Brauner Cc: Arnd Bergmann Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-2-gnoack@google.com Signed-off-by: Mickaël Salaün --- include/uapi/linux/landlock.h | 38 +++- security/landlock/fs.c | 225 ++++++++++++++++++- 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 | 5 +- 6 files changed, 258 insertions(+), 16 deletions(-) diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 25c8d7677539..68625e728f43 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -128,7 +128,7 @@ struct landlock_net_port_attr { * files and directories. Files or directories opened before the sandboxing * are not subject to these restrictions. * - * A file can only receive these access rights: + * The following access rights apply only to files: * * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file. * - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that @@ -138,12 +138,13 @@ struct landlock_net_port_attr { * - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access. * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`, * :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with - * ``O_TRUNC``. Whether an opened file can be truncated with - * :manpage:`ftruncate(2)` is determined during :manpage:`open(2)`, in the - * same way as read and write permissions are checked during - * :manpage:`open(2)` using %LANDLOCK_ACCESS_FS_READ_FILE and - * %LANDLOCK_ACCESS_FS_WRITE_FILE. This access right is available since the - * third version of the Landlock ABI. + * ``O_TRUNC``. This access right is available since the third version of the + * Landlock ABI. + * + * Whether an opened file can be truncated with :manpage:`ftruncate(2)` or used + * with `ioctl(2)` is determined during :manpage:`open(2)`, in the same way as + * read and write permissions are checked during :manpage:`open(2)` using + * %LANDLOCK_ACCESS_FS_READ_FILE and %LANDLOCK_ACCESS_FS_WRITE_FILE. * * A directory can receive access rights related to files or directories. The * following access right is applied to the directory itself, and the @@ -198,13 +199,33 @@ struct landlock_net_port_attr { * If multiple requirements are not met, the ``EACCES`` error code takes * precedence over ``EXDEV``. * + * The following access right applies both to files and directories: + * + * - %LANDLOCK_ACCESS_FS_IOCTL_DEV: Invoke :manpage:`ioctl(2)` commands on an opened + * character or block device. + * + * This access right applies to all `ioctl(2)` commands implemented by device + * drivers. However, the following common IOCTL commands continue to be + * invokable independent of the %LANDLOCK_ACCESS_FS_IOCTL_DEV right: + * + * * IOCTL commands targeting file descriptors (``FIOCLEX``, ``FIONCLEX``), + * * IOCTL commands targeting file descriptions (``FIONBIO``, ``FIOASYNC``), + * * IOCTL commands targeting file systems (``FIFREEZE``, ``FITHAW``, + * ``FIGETBSZ``, ``FS_IOC_GETFSUUID``, ``FS_IOC_GETFSSYSFSPATH``) + * * Some IOCTL commands which do not make sense when used with devices, but + * whose implementations are safe and return the right error codes + * (``FS_IOC_FIEMAP``, ``FICLONE``, ``FICLONERANGE``, ``FIDEDUPERANGE``) + * + * This access right is available since the fifth version of the Landlock + * ABI. + * * .. 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:`fcntl(2)`, :manpage:`access(2)`. * Future Landlock evolutions will enable to restrict them. */ /* clang-format off */ @@ -223,6 +244,7 @@ struct landlock_net_port_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_IOCTL_DEV (1ULL << 15) /* clang-format on */ /** diff --git a/security/landlock/fs.c b/security/landlock/fs.c index c15559432d3d..22d8b7c28074 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -5,8 +5,11 @@ * Copyright © 2016-2020 Mickaël Salaün * Copyright © 2018-2020 ANSSI * Copyright © 2021-2022 Microsoft Corporation + * Copyright © 2022 Günther Noack + * Copyright © 2023-2024 Google LLC */ +#include #include #include #include @@ -14,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -29,6 +33,7 @@ #include #include #include +#include #include #include "common.h" @@ -84,6 +89,160 @@ static const struct landlock_object_underops landlock_fs_underops = { .release = release_inode }; +/* IOCTL helpers */ + +/** + * is_masked_device_ioctl - Determine whether an IOCTL command is always + * permitted with Landlock for device files. These commands can not be + * restricted on device files by enforcing a Landlock policy. + * + * @cmd: The IOCTL command that is supposed to be run. + * + * By default, any IOCTL on a device file requires the + * LANDLOCK_ACCESS_FS_IOCTL_DEV right. However, we blanket-permit some + * commands, if: + * + * 1. The command is implemented in fs/ioctl.c's do_vfs_ioctl(), + * not in f_ops->unlocked_ioctl() or f_ops->compat_ioctl(). + * + * 2. The command is harmless when invoked on devices. + * + * We also permit commands that do not make sense for devices, but where the + * do_vfs_ioctl() implementation returns a more conventional error code. + * + * Any new IOCTL commands that are implemented in fs/ioctl.c's do_vfs_ioctl() + * should be considered for inclusion here. + * + * Returns: true if the IOCTL @cmd can not be restricted with Landlock for + * device files. + */ +static __attribute_const__ bool is_masked_device_ioctl(const unsigned int cmd) +{ + switch (cmd) { + /* + * FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC manipulate the FD's + * close-on-exec and the file's buffered-IO and async flags. These + * operations are also available through fcntl(2), and are + * unconditionally permitted in Landlock. + */ + case FIOCLEX: + case FIONCLEX: + case FIONBIO: + case FIOASYNC: + /* + * FIOQSIZE queries the size of a regular file, directory, or link. + * + * We still permit it, because it always returns -ENOTTY for + * other file types. + */ + case FIOQSIZE: + /* + * FIFREEZE and FITHAW freeze and thaw the file system which the + * given file belongs to. Requires CAP_SYS_ADMIN. + * + * These commands operate on the file system's superblock rather + * than on the file itself. The same operations can also be + * done through any other file or directory on the same file + * system, so it is safe to permit these. + */ + case FIFREEZE: + case FITHAW: + /* + * FS_IOC_FIEMAP queries information about the allocation of + * blocks within a file. + * + * This IOCTL command only makes sense for regular files and is + * not implemented by devices. It is harmless to permit. + */ + case FS_IOC_FIEMAP: + /* + * FIGETBSZ queries the file system's block size for a file or + * directory. + * + * This command operates on the file system's superblock rather + * than on the file itself. The same operation can also be done + * through any other file or directory on the same file system, + * so it is safe to permit it. + */ + case FIGETBSZ: + /* + * FICLONE, FICLONERANGE and FIDEDUPERANGE make files share + * their underlying storage ("reflink") between source and + * destination FDs, on file systems which support that. + * + * These IOCTL commands only apply to regular files + * and are harmless to permit for device files. + */ + case FICLONE: + case FICLONERANGE: + case FIDEDUPERANGE: + /* + * FS_IOC_GETFSUUID and FS_IOC_GETFSSYSFSPATH both operate on + * the file system superblock, not on the specific file, so + * these operations are available through any other file on the + * same file system as well. + */ + case FS_IOC_GETFSUUID: + case FS_IOC_GETFSSYSFSPATH: + return true; + + /* + * FIONREAD, FS_IOC_GETFLAGS, FS_IOC_SETFLAGS, FS_IOC_FSGETXATTR and + * FS_IOC_FSSETXATTR are forwarded to device implementations. + */ + + /* + * file_ioctl() commands (FIBMAP, FS_IOC_RESVSP, FS_IOC_RESVSP64, + * FS_IOC_UNRESVSP, FS_IOC_UNRESVSP64 and FS_IOC_ZERO_RANGE) are + * forwarded to device implementations, so not permitted. + */ + + /* Other commands are guarded by the access right. */ + default: + return false; + } +} + +/* + * is_masked_device_ioctl_compat - same as the helper above, but checking the + * "compat" IOCTL commands. + * + * The IOCTL commands with special handling in compat-mode should behave the + * same as their non-compat counterparts. + */ +static __attribute_const__ bool +is_masked_device_ioctl_compat(const unsigned int cmd) +{ + switch (cmd) { + /* FICLONE is permitted, same as in the non-compat variant. */ + case FICLONE: + return true; + +#if defined(CONFIG_X86_64) + /* + * FS_IOC_RESVSP_32, FS_IOC_RESVSP64_32, FS_IOC_UNRESVSP_32, + * FS_IOC_UNRESVSP64_32, FS_IOC_ZERO_RANGE_32: not blanket-permitted, + * for consistency with their non-compat variants. + */ + case FS_IOC_RESVSP_32: + case FS_IOC_RESVSP64_32: + case FS_IOC_UNRESVSP_32: + case FS_IOC_UNRESVSP64_32: + case FS_IOC_ZERO_RANGE_32: +#endif + + /* + * FS_IOC32_GETFLAGS, FS_IOC32_SETFLAGS are forwarded to their device + * implementations. + */ + case FS_IOC32_GETFLAGS: + case FS_IOC32_SETFLAGS: + return false; + default: + return is_masked_device_ioctl(cmd); + } +} + /* Ruleset management */ static struct landlock_object *get_inode_object(struct inode *const inode) @@ -148,7 +307,8 @@ retry: 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_IOCTL_DEV) /* clang-format on */ /* @@ -1332,11 +1492,18 @@ static int hook_file_alloc_security(struct file *const file) return 0; } +static bool is_device(const struct file *const file) +{ + const struct inode *inode = file_inode(file); + + return S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode); +} + 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; + access_mask_t open_access_request, full_access_request, allowed_access, + optional_access; const struct landlock_ruleset *const dom = get_fs_domain(landlock_cred(file->f_cred)->domain); @@ -1354,6 +1521,10 @@ static int hook_file_open(struct file *const file) * We look up more access than what we immediately need for open(), so * that we can later authorize operations on opened files. */ + optional_access = LANDLOCK_ACCESS_FS_TRUNCATE; + if (is_device(file)) + optional_access |= LANDLOCK_ACCESS_FS_IOCTL_DEV; + full_access_request = open_access_request | optional_access; if (is_access_to_paths_allowed( @@ -1410,6 +1581,52 @@ static int hook_file_truncate(struct file *const file) return -EACCES; } +static int hook_file_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + access_mask_t allowed_access = landlock_file(file)->allowed_access; + + /* + * It is the access rights at the time of opening the file which + * determine whether IOCTL can be used on the opened file later. + * + * The access right is attached to the opened file in hook_file_open(). + */ + if (allowed_access & LANDLOCK_ACCESS_FS_IOCTL_DEV) + return 0; + + if (!is_device(file)) + return 0; + + if (is_masked_device_ioctl(cmd)) + return 0; + + return -EACCES; +} + +static int hook_file_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + access_mask_t allowed_access = landlock_file(file)->allowed_access; + + /* + * It is the access rights at the time of opening the file which + * determine whether IOCTL can be used on the opened file later. + * + * The access right is attached to the opened file in hook_file_open(). + */ + if (allowed_access & LANDLOCK_ACCESS_FS_IOCTL_DEV) + return 0; + + if (!is_device(file)) + return 0; + + if (is_masked_device_ioctl_compat(cmd)) + return 0; + + return -EACCES; +} + static struct security_hook_list landlock_hooks[] __ro_after_init = { LSM_HOOK_INIT(inode_free_security, hook_inode_free_security), @@ -1432,6 +1649,8 @@ static struct security_hook_list landlock_hooks[] __ro_after_init = { 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), + LSM_HOOK_INIT(file_ioctl, hook_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, hook_file_ioctl_compat), }; __init void landlock_add_fs_hooks(void) diff --git a/security/landlock/limits.h b/security/landlock/limits.h index 93c9c6f91556..20fdb5ff3514 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_IOCTL_DEV #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) #define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS) #define LANDLOCK_SHIFT_ACCESS_FS 0 diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 6788e73b6681..03b470f5a85a 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -149,7 +149,7 @@ static const struct file_operations ruleset_fops = { .write = fop_dummy_write, }; -#define LANDLOCK_ABI_VERSION 4 +#define LANDLOCK_ABI_VERSION 5 /** * 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 a6f89aaea77d..3c1e9f35b531 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(4, landlock_create_ruleset(NULL, 0, + ASSERT_EQ(5, 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 27744524df51..17b00e6c778d 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -536,9 +536,10 @@ 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_IOCTL_DEV) -#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE +#define ACCESS_LAST LANDLOCK_ACCESS_FS_IOCTL_DEV #define ACCESS_ALL ( \ ACCESS_FILE | \ From 3ecf19e56843a6fe65f109c773728c36d220f947 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:13 +0000 Subject: [PATCH 03/13] selftests/landlock: Test IOCTL support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Exercises Landlock's IOCTL feature in different combinations of handling and permitting the LANDLOCK_ACCESS_FS_IOCTL_DEV right, and in different combinations of using files and directories. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-3-gnoack@google.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 192 ++++++++++++++++++++- 1 file changed, 189 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 17b00e6c778d..fd7793b413d1 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -8,6 +8,7 @@ */ #define _GNU_SOURCE +#include #include #include #include @@ -16,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -24,6 +26,12 @@ #include #include +/* + * Intentionally included last to work around header conflict. + * See https://sourceware.org/glibc/wiki/Synchronizing_Headers. + */ +#include + #include "common.h" #ifndef renameat2 @@ -744,6 +752,9 @@ static int create_ruleset(struct __test_metadata *const _metadata, } for (i = 0; rules[i].path; i++) { + if (!rules[i].access) + continue; + add_path_beneath(_metadata, ruleset_fd, rules[i].access, rules[i].path); } @@ -3452,7 +3463,7 @@ TEST_F_FORK(layout1, truncate_unhandled) LANDLOCK_ACCESS_FS_WRITE_FILE; int ruleset_fd; - /* Enable Landlock. */ + /* Enables Landlock. */ ruleset_fd = create_ruleset(_metadata, handled, rules); ASSERT_LE(0, ruleset_fd); @@ -3535,7 +3546,7 @@ TEST_F_FORK(layout1, truncate) LANDLOCK_ACCESS_FS_TRUNCATE; int ruleset_fd; - /* Enable Landlock. */ + /* Enables Landlock. */ ruleset_fd = create_ruleset(_metadata, handled, rules); ASSERT_LE(0, ruleset_fd); @@ -3761,7 +3772,7 @@ TEST_F_FORK(ftruncate, open_and_ftruncate) }; int fd, ruleset_fd; - /* Enable Landlock. */ + /* Enables Landlock. */ ruleset_fd = create_ruleset(_metadata, variant->handled, rules); ASSERT_LE(0, ruleset_fd); enforce_ruleset(_metadata, ruleset_fd); @@ -3854,6 +3865,181 @@ TEST(memfd_ftruncate) ASSERT_EQ(0, close(fd)); } +static int test_fionread_ioctl(int fd) +{ + size_t sz = 0; + + if (ioctl(fd, FIONREAD, &sz) < 0 && errno == EACCES) + return errno; + return 0; +} + +/* clang-format off */ +FIXTURE(ioctl) {}; + +FIXTURE_SETUP(ioctl) {}; + +FIXTURE_TEARDOWN(ioctl) {}; +/* clang-format on */ + +FIXTURE_VARIANT(ioctl) +{ + const __u64 handled; + const __u64 allowed; + const mode_t open_mode; + /* + * FIONREAD is used as a characteristic device-specific IOCTL command. + * It is implemented in fs/ioctl.c for regular files, + * but we do not blanket-permit it for devices. + */ + const int expected_fionread_result; +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_none) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_IOCTL_DEV, + .allowed = 0, + .open_mode = O_RDWR, + .expected_fionread_result = EACCES, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ioctl, handled_i_allowed_i) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_IOCTL_DEV, + .allowed = LANDLOCK_ACCESS_FS_IOCTL_DEV, + .open_mode = O_RDWR, + .expected_fionread_result = 0, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ioctl, unhandled) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_EXECUTE, + .allowed = LANDLOCK_ACCESS_FS_EXECUTE, + .open_mode = O_RDWR, + .expected_fionread_result = 0, +}; + +TEST_F_FORK(ioctl, handle_dir_access_file) +{ + const int flag = 0; + const struct rule rules[] = { + { + .path = "/dev", + .access = variant->allowed, + }, + {}, + }; + int file_fd, ruleset_fd; + + /* Enables Landlock. */ + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + file_fd = open("/dev/zero", variant->open_mode); + ASSERT_LE(0, file_fd); + + /* Checks that IOCTL commands return the expected errors. */ + EXPECT_EQ(variant->expected_fionread_result, + test_fionread_ioctl(file_fd)); + + /* Checks that unrestrictable commands are unrestricted. */ + EXPECT_EQ(0, ioctl(file_fd, FIOCLEX)); + EXPECT_EQ(0, ioctl(file_fd, FIONCLEX)); + EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag)); + EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag)); + EXPECT_EQ(0, ioctl(file_fd, FIGETBSZ, &flag)); + + ASSERT_EQ(0, close(file_fd)); +} + +TEST_F_FORK(ioctl, handle_dir_access_dir) +{ + const int flag = 0; + const struct rule rules[] = { + { + .path = "/dev", + .access = variant->allowed, + }, + {}, + }; + int dir_fd, ruleset_fd; + + /* Enables Landlock. */ + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* + * Ignore variant->open_mode for this test, as we intend to open a + * directory. If the directory can not be opened, the variant is + * infeasible to test with an opened directory. + */ + dir_fd = open("/dev", O_RDONLY); + if (dir_fd < 0) + return; + + /* + * Checks that IOCTL commands return the expected errors. + * We do not use the expected values from the fixture here. + * + * When using IOCTL on a directory, no Landlock restrictions apply. + */ + EXPECT_EQ(0, test_fionread_ioctl(dir_fd)); + + /* Checks that unrestrictable commands are unrestricted. */ + EXPECT_EQ(0, ioctl(dir_fd, FIOCLEX)); + EXPECT_EQ(0, ioctl(dir_fd, FIONCLEX)); + EXPECT_EQ(0, ioctl(dir_fd, FIONBIO, &flag)); + EXPECT_EQ(0, ioctl(dir_fd, FIOASYNC, &flag)); + EXPECT_EQ(0, ioctl(dir_fd, FIGETBSZ, &flag)); + + ASSERT_EQ(0, close(dir_fd)); +} + +TEST_F_FORK(ioctl, handle_file_access_file) +{ + const int flag = 0; + const struct rule rules[] = { + { + .path = "/dev/zero", + .access = variant->allowed, + }, + {}, + }; + int file_fd, ruleset_fd; + + /* Enables Landlock. */ + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + file_fd = open("/dev/zero", variant->open_mode); + ASSERT_LE(0, file_fd) + { + TH_LOG("Failed to open /dev/zero: %s", strerror(errno)); + } + + /* Checks that IOCTL commands return the expected errors. */ + EXPECT_EQ(variant->expected_fionread_result, + test_fionread_ioctl(file_fd)); + + /* Checks that unrestrictable commands are unrestricted. */ + EXPECT_EQ(0, ioctl(file_fd, FIOCLEX)); + EXPECT_EQ(0, ioctl(file_fd, FIONCLEX)); + EXPECT_EQ(0, ioctl(file_fd, FIONBIO, &flag)); + EXPECT_EQ(0, ioctl(file_fd, FIOASYNC, &flag)); + EXPECT_EQ(0, ioctl(file_fd, FIGETBSZ, &flag)); + + ASSERT_EQ(0, close(file_fd)); +} + /* clang-format off */ FIXTURE(layout1_bind) {}; /* clang-format on */ From dd6d32afdf5f1869a8f543e8efdd191f7e4b0368 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:14 +0000 Subject: [PATCH 04/13] selftests/landlock: Test IOCTL with memfds MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Because the LANDLOCK_ACCESS_FS_IOCTL_DEV right is associated with the opened file during open(2), IOCTLs are supposed to work with files which are opened by means other than open(2). Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-4-gnoack@google.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 44 ++++++++++++++++++---- 1 file changed, 36 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index fd7793b413d1..193dc58bac7a 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3849,20 +3849,48 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes) ASSERT_EQ(0, close(socket_fds[1])); } -TEST(memfd_ftruncate) +/* Invokes the FS_IOC_GETFLAGS IOCTL and returns its errno or 0. */ +static int test_fs_ioc_getflags_ioctl(int fd) { - int fd; + uint32_t flags; - fd = memfd_create("name", MFD_CLOEXEC); - ASSERT_LE(0, fd); + if (ioctl(fd, FS_IOC_GETFLAGS, &flags) < 0) + return errno; + return 0; +} + +TEST(memfd_ftruncate_and_ioctl) +{ + const struct landlock_ruleset_attr attr = { + .handled_access_fs = ACCESS_ALL, + }; + int ruleset_fd, fd, i; /* - * Checks that ftruncate is permitted on file descriptors that are - * created in ways other than open(2). + * We exercise the same test both with and without Landlock enabled, to + * ensure that it behaves the same in both cases. */ - EXPECT_EQ(0, test_ftruncate(fd)); + for (i = 0; i < 2; i++) { + /* Creates a new memfd. */ + fd = memfd_create("name", MFD_CLOEXEC); + ASSERT_LE(0, fd); - ASSERT_EQ(0, close(fd)); + /* + * Checks that operations associated with the opened file + * (ftruncate, ioctl) are permitted on file descriptors that are + * created in ways other than open(2). + */ + EXPECT_EQ(0, test_ftruncate(fd)); + EXPECT_EQ(0, test_fs_ioc_getflags_ioctl(fd)); + + ASSERT_EQ(0, close(fd)); + + /* Enables Landlock. */ + ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + } } static int test_fionread_ioctl(int fd) From 7954a1d155975a3fbc9570151358738f59605121 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:15 +0000 Subject: [PATCH 05/13] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ioctl(2) and ftruncate(2) operations on files opened with O_PATH should always return EBADF, independent of the LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL_DEV access rights in that file hierarchy. Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-5-gnoack@google.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 40 ++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 193dc58bac7a..cb6e9330fcf5 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3902,6 +3902,46 @@ static int test_fionread_ioctl(int fd) return 0; } +TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl) +{ + const struct landlock_ruleset_attr attr = { + .handled_access_fs = ACCESS_ALL, + }; + int ruleset_fd, fd; + + /* + * Checks that for files opened with O_PATH, both ioctl(2) and + * ftruncate(2) yield EBADF, as it is documented in open(2) for the + * O_PATH flag. + */ + fd = open(dir_s1d1, O_PATH | O_CLOEXEC); + ASSERT_LE(0, fd); + + EXPECT_EQ(EBADF, test_ftruncate(fd)); + EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd)); + + ASSERT_EQ(0, close(fd)); + + /* Enables Landlock. */ + ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* + * Checks that after enabling Landlock, + * - the file can still be opened with O_PATH + * - both ioctl and truncate still yield EBADF (not EACCES). + */ + fd = open(dir_s1d1, O_PATH | O_CLOEXEC); + ASSERT_LE(0, fd); + + EXPECT_EQ(EBADF, test_ftruncate(fd)); + EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd)); + + ASSERT_EQ(0, close(fd)); +} + /* clang-format off */ FIXTURE(ioctl) {}; From 56ffd377c7abe670ba5f024328e0c0fc0f49920c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:16 +0000 Subject: [PATCH 06/13] selftests/landlock: Test IOCTLs on named pipes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Named pipes should behave like pipes created with pipe(2), so we don't want to restrict IOCTLs on them. Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-6-gnoack@google.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 43 ++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index cb6e9330fcf5..b133020c7761 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3942,6 +3942,49 @@ TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl) ASSERT_EQ(0, close(fd)); } +/* + * Named pipes are not governed by the LANDLOCK_ACCESS_FS_IOCTL_DEV right, + * because they are not character or block devices. + */ +TEST_F_FORK(layout1, named_pipe_ioctl) +{ + pid_t child_pid; + int fd, ruleset_fd; + const char *const path = file1_s1d1; + const struct landlock_ruleset_attr attr = { + .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV, + }; + + ASSERT_EQ(0, unlink(path)); + ASSERT_EQ(0, mkfifo(path, 0600)); + + /* Enables Landlock. */ + ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* The child process opens the pipe for writing. */ + child_pid = fork(); + ASSERT_NE(-1, child_pid); + if (child_pid == 0) { + fd = open(path, O_WRONLY); + close(fd); + exit(0); + } + + fd = open(path, O_RDONLY); + ASSERT_LE(0, fd); + + /* FIONREAD is implemented by pipefifo_fops. */ + EXPECT_EQ(0, test_fionread_ioctl(fd)); + + ASSERT_EQ(0, close(fd)); + ASSERT_EQ(0, unlink(path)); + + ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0)); +} + /* clang-format off */ FIXTURE(ioctl) {}; From f83d51a5bdfe5ab56c27fd5dfe01c613b37e2dad Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:17 +0000 Subject: [PATCH 07/13] selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The LANDLOCK_ACCESS_FS_IOCTL_DEV right should have no effect on the use of named UNIX domain sockets. Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-7-gnoack@google.com [mic: Add missing stddef.h for offsetof()] Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 53 ++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index b133020c7761..8443f329ac7c 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -21,8 +22,10 @@ #include #include #include +#include #include #include +#include #include #include @@ -3985,6 +3988,56 @@ TEST_F_FORK(layout1, named_pipe_ioctl) ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0)); } +/* For named UNIX domain sockets, no IOCTL restrictions apply. */ +TEST_F_FORK(layout1, named_unix_domain_socket_ioctl) +{ + const char *const path = file1_s1d1; + int srv_fd, cli_fd, ruleset_fd; + socklen_t size; + struct sockaddr_un srv_un, cli_un; + const struct landlock_ruleset_attr attr = { + .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV, + }; + + /* Sets up a server */ + srv_un.sun_family = AF_UNIX; + strncpy(srv_un.sun_path, path, sizeof(srv_un.sun_path)); + + ASSERT_EQ(0, unlink(path)); + srv_fd = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_LE(0, srv_fd); + + size = offsetof(struct sockaddr_un, sun_path) + strlen(srv_un.sun_path); + ASSERT_EQ(0, bind(srv_fd, (struct sockaddr *)&srv_un, size)); + ASSERT_EQ(0, listen(srv_fd, 10 /* qlen */)); + + /* Enables Landlock. */ + ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* Sets up a client connection to it */ + cli_un.sun_family = AF_UNIX; + cli_fd = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_LE(0, cli_fd); + + size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path); + ASSERT_EQ(0, bind(cli_fd, (struct sockaddr *)&cli_un, size)); + + bzero(&cli_un, sizeof(cli_un)); + cli_un.sun_family = AF_UNIX; + strncpy(cli_un.sun_path, path, sizeof(cli_un.sun_path)); + size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path); + + ASSERT_EQ(0, connect(cli_fd, (struct sockaddr *)&cli_un, size)); + + /* FIONREAD and other IOCTLs should not be forbidden. */ + EXPECT_EQ(0, test_fionread_ioctl(cli_fd)); + + ASSERT_EQ(0, close(cli_fd)); +} + /* clang-format off */ FIXTURE(ioctl) {}; From bce605e0cfa55da513b672500dd838be1ef41de7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:18 +0000 Subject: [PATCH 08/13] selftests/landlock: Exhaustive test for the IOCTL allow-list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This test checks all IOCTL commands implemented in do_vfs_ioctl(). Test coverage for security/landlock is 90.9% of 722 lines according to gcc/gcov-13. Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-8-gnoack@google.com [mic: Add test coverage] Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 114 +++++++++++++++++++++ 1 file changed, 114 insertions(+) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 8443f329ac7c..6b5a9ff88c3d 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -3945,6 +3946,119 @@ TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl) ASSERT_EQ(0, close(fd)); } +/* + * ioctl_error - generically call the given ioctl with a pointer to a + * sufficiently large zeroed-out memory region. + * + * Returns the IOCTLs error, or 0. + */ +static int ioctl_error(struct __test_metadata *const _metadata, int fd, + unsigned int cmd) +{ + char buf[128]; /* sufficiently large */ + int res, stdinbak_fd; + + /* + * Depending on the IOCTL command, parts of the zeroed-out buffer might + * be interpreted as file descriptor numbers. We do not want to + * accidentally operate on file descriptor 0 (stdin), so we temporarily + * move stdin to a different FD and close FD 0 for the IOCTL call. + */ + stdinbak_fd = dup(0); + ASSERT_LT(0, stdinbak_fd); + ASSERT_EQ(0, close(0)); + + /* Invokes the IOCTL with a zeroed-out buffer. */ + bzero(&buf, sizeof(buf)); + res = ioctl(fd, cmd, &buf); + + /* Restores the old FD 0 and closes the backup FD. */ + ASSERT_EQ(0, dup2(stdinbak_fd, 0)); + ASSERT_EQ(0, close(stdinbak_fd)); + + if (res < 0) + return errno; + + return 0; +} + +/* Define some linux/falloc.h IOCTL commands which are not available in uapi headers. */ +struct space_resv { + __s16 l_type; + __s16 l_whence; + __s64 l_start; + __s64 l_len; /* len == 0 means until end of file */ + __s32 l_sysid; + __u32 l_pid; + __s32 l_pad[4]; /* reserved area */ +}; + +#define FS_IOC_RESVSP _IOW('X', 40, struct space_resv) +#define FS_IOC_UNRESVSP _IOW('X', 41, struct space_resv) +#define FS_IOC_RESVSP64 _IOW('X', 42, struct space_resv) +#define FS_IOC_UNRESVSP64 _IOW('X', 43, struct space_resv) +#define FS_IOC_ZERO_RANGE _IOW('X', 57, struct space_resv) + +/* + * Tests a series of blanket-permitted and denied IOCTLs. + */ +TEST_F_FORK(layout1, blanket_permitted_ioctls) +{ + const struct landlock_ruleset_attr attr = { + .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV, + }; + int ruleset_fd, fd; + + /* Enables Landlock. */ + ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd = open("/dev/null", O_RDWR | O_CLOEXEC); + ASSERT_LE(0, fd); + + /* + * Checks permitted commands. + * These ones may return errors, but should not be blocked by Landlock. + */ + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIOCLEX)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIONCLEX)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIONBIO)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIOASYNC)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIOQSIZE)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIFREEZE)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FITHAW)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FS_IOC_FIEMAP)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIGETBSZ)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FICLONE)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FICLONERANGE)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FIDEDUPERANGE)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FS_IOC_GETFSUUID)); + EXPECT_NE(EACCES, ioctl_error(_metadata, fd, FS_IOC_GETFSSYSFSPATH)); + + /* + * Checks blocked commands. + * A call to a blocked IOCTL command always returns EACCES. + */ + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FIONREAD)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_GETFLAGS)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_SETFLAGS)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_FSGETXATTR)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_FSSETXATTR)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FIBMAP)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_RESVSP)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_RESVSP64)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_UNRESVSP)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_UNRESVSP64)); + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, FS_IOC_ZERO_RANGE)); + + /* Default case is also blocked. */ + EXPECT_EQ(EACCES, ioctl_error(_metadata, fd, 0xc00ffeee)); + + ASSERT_EQ(0, close(fd)); +} + /* * Named pipes are not governed by the LANDLOCK_ACCESS_FS_IOCTL_DEV right, * because they are not character or block devices. From cd13738d44c9863ce54243fdcc2d228233f23355 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:19 +0000 Subject: [PATCH 09/13] samples/landlock: Add support for LANDLOCK_ACCESS_FS_IOCTL_DEV MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add IOCTL support to the Landlock sample tool. The IOCTL right is grouped with the read-write rights in the sample tool, as some IOCTL requests provide features that mutate state. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-9-gnoack@google.com Signed-off-by: Mickaël Salaün --- samples/landlock/sandboxer.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 8b8ecd65c28c..e8223c3e781a 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -81,7 +81,8 @@ static int parse_path(char *env_path, const char ***const path_list) 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_IOCTL_DEV) /* clang-format on */ @@ -202,11 +203,12 @@ out_free_name: LANDLOCK_ACCESS_FS_MAKE_BLOCK | \ LANDLOCK_ACCESS_FS_MAKE_SYM | \ LANDLOCK_ACCESS_FS_REFER | \ - LANDLOCK_ACCESS_FS_TRUNCATE) + LANDLOCK_ACCESS_FS_TRUNCATE | \ + LANDLOCK_ACCESS_FS_IOCTL_DEV) /* clang-format on */ -#define LANDLOCK_ABI_LAST 4 +#define LANDLOCK_ABI_LAST 5 int main(const int argc, char *const argv[], char *const *const envp) { @@ -320,6 +322,11 @@ int main(const int argc, char *const argv[], char *const *const envp) ruleset_attr.handled_access_net &= ~(LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP); + __attribute__((fallthrough)); + case 4: + /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ + ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; + fprintf(stderr, "Hint: You should update the running kernel " "to leverage Landlock features " From a3746da89faf985132e428056d147b743b7174e4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:20 +0000 Subject: [PATCH 10/13] landlock: Document IOCTL support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the paragraph above the fallback logic, use the shorter phrasing from the landlock(7) man page. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-10-gnoack@google.com [mic: Update date, and fix redundant "access"] Signed-off-by: Mickaël Salaün --- Documentation/userspace-api/landlock.rst | 78 +++++++++++++++++++----- 1 file changed, 62 insertions(+), 16 deletions(-) diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst index 9dd636aaa829..07b63aec56fa 100644 --- a/Documentation/userspace-api/landlock.rst +++ b/Documentation/userspace-api/landlock.rst @@ -8,7 +8,7 @@ Landlock: unprivileged access control ===================================== :Author: Mickaël Salaün -:Date: October 2023 +:Date: April 2024 The goal of Landlock is to enable to restrict ambient rights (e.g. global filesystem or network access) for a set of processes. Because Landlock @@ -76,7 +76,8 @@ to be explicit about the denied-by-default access rights. LANDLOCK_ACCESS_FS_MAKE_BLOCK | LANDLOCK_ACCESS_FS_MAKE_SYM | LANDLOCK_ACCESS_FS_REFER | - LANDLOCK_ACCESS_FS_TRUNCATE, + LANDLOCK_ACCESS_FS_TRUNCATE | + LANDLOCK_ACCESS_FS_IOCTL_DEV, .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP, @@ -85,10 +86,10 @@ to be explicit about the denied-by-default access rights. Because we may not know on which kernel version an application will be executed, it is safer to follow a best-effort security approach. Indeed, we should try to protect users as much as possible whatever the kernel they are -using. To avoid binary enforcement (i.e. either all security features or -none), we can leverage a dedicated Landlock command to get the current version -of the Landlock ABI and adapt the handled accesses. Let's check if we should -remove access rights which are only supported in higher versions of the ABI. +using. + +To be compatible with older Linux versions, we detect the available Landlock ABI +version, and only use the available subset of access rights: .. code-block:: c @@ -114,6 +115,10 @@ remove access rights which are only supported in higher versions of the ABI. ruleset_attr.handled_access_net &= ~(LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP); + __attribute__((fallthrough)); + case 4: + /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ + ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; } This enables to create an inclusive ruleset that will contain our rules. @@ -225,6 +230,7 @@ access rights per directory enables to change the location of such directory without relying on the destination directory access rights (except those that are required for this operation, see ``LANDLOCK_ACCESS_FS_REFER`` documentation). + Having self-sufficient hierarchies also helps to tighten the required access rights to the minimal set of data. This also helps avoid sinkhole directories, i.e. directories where data can be linked to but not linked from. However, @@ -318,18 +324,26 @@ It should also be noted that truncating files does not require the system call, this can also be done through :manpage:`open(2)` with the flags ``O_RDONLY | O_TRUNC``. -When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE`` -right is associated with the newly created file descriptor and will be used for -subsequent truncation attempts using :manpage:`ftruncate(2)`. The behavior is -similar to opening a file for reading or writing, where permissions are checked -during :manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and +The truncate right is associated with the opened file (see below). + +Rights associated with file descriptors +--------------------------------------- + +When opening a file, the availability of the ``LANDLOCK_ACCESS_FS_TRUNCATE`` and +``LANDLOCK_ACCESS_FS_IOCTL_DEV`` rights is associated with the newly created +file descriptor and will be used for subsequent truncation and ioctl attempts +using :manpage:`ftruncate(2)` and :manpage:`ioctl(2)`. The behavior is similar +to opening a file for reading or writing, where permissions are checked during +:manpage:`open(2)`, but not during the subsequent :manpage:`read(2)` and :manpage:`write(2)` calls. -As a consequence, it is possible to have multiple open file descriptors for the -same file, where one grants the right to truncate the file and the other does -not. It is also possible to pass such file descriptors between processes, -keeping their Landlock properties, even when these processes do not have an -enforced Landlock ruleset. +As a consequence, it is possible that a process has multiple open file +descriptors referring to the same file, but Landlock enforces different things +when operating with these file descriptors. This can happen when a Landlock +ruleset gets enforced and the process keeps file descriptors which were opened +both before and after the enforcement. It is also possible to pass such file +descriptors between processes, keeping their Landlock properties, even when some +of the involved processes do not have an enforced Landlock ruleset. Compatibility ============= @@ -458,6 +472,28 @@ Memory usage Kernel memory allocated to create rulesets is accounted and can be restricted by the Documentation/admin-guide/cgroup-v1/memory.rst. +IOCTL support +------------- + +The ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right restricts the use of +:manpage:`ioctl(2)`, but it only applies to *newly opened* device files. This +means specifically that pre-existing file descriptors like stdin, stdout and +stderr are unaffected. + +Users should be aware that TTY devices have traditionally permitted to control +other processes on the same TTY through the ``TIOCSTI`` and ``TIOCLINUX`` IOCTL +commands. Both of these require ``CAP_SYS_ADMIN`` on modern Linux systems, but +the behavior is configurable for ``TIOCSTI``. + +On older systems, it is therefore recommended to close inherited TTY file +descriptors, or to reopen them from ``/proc/self/fd/*`` without the +``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right, if possible. + +Landlock's IOCTL support is coarse-grained at the moment, but may become more +fine-grained in the future. Until then, users are advised to establish the +guarantees that they need through the file hierarchy, by only allowing the +``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right on files where it is really required. + Previous limitations ==================== @@ -495,6 +531,16 @@ bind and connect actions to only a set of allowed ports thanks to the new ``LANDLOCK_ACCESS_NET_BIND_TCP`` and ``LANDLOCK_ACCESS_NET_CONNECT_TCP`` access rights. +IOCTL (ABI < 5) +--------------- + +IOCTL operations could not be denied before the fifth Landlock ABI, so +:manpage:`ioctl(2)` is always allowed when using a kernel that only supports an +earlier ABI. + +Starting with the Landlock ABI version 5, it is possible to restrict the use of +:manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right. + .. _kernel_support: Kernel support From 943aa818cd6606a1385130bc72f5066b82fe4346 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:21 +0000 Subject: [PATCH 11/13] MAINTAINERS: Notify Landlock maintainers about changes to fs/ioctl.c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Landlock needs to track changes to do_vfs_ioctl() when new IOCTL implementations are added to it. Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-11-gnoack@google.com Signed-off-by: Mickaël Salaün --- MAINTAINERS | 1 + 1 file changed, 1 insertion(+) diff --git a/MAINTAINERS b/MAINTAINERS index 28e20975c26f..b01345abadb2 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12220,6 +12220,7 @@ W: https://landlock.io T: git https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux.git F: Documentation/security/landlock.rst F: Documentation/userspace-api/landlock.rst +F: fs/ioctl.c F: include/uapi/linux/landlock.h F: samples/landlock/ F: security/landlock/ From d1654fd98be731b08d2b7b857ef2026df6767e3d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 19 Apr 2024 16:11:22 +0000 Subject: [PATCH 12/13] fs/ioctl: Add a comment to keep the logic in sync with LSM policies MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Landlock's IOCTL support needs to partially replicate the list of IOCTLs from do_vfs_ioctl(). The list of commands implemented in do_vfs_ioctl() should be kept in sync with Landlock's IOCTL policies. Suggested-by: Paul Moore Suggested-by: Mickaël Salaün Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-12-gnoack@google.com Signed-off-by: Mickaël Salaün --- fs/ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ioctl.c b/fs/ioctl.c index fb0628e680c4..64776891120c 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -796,6 +796,9 @@ static int ioctl_get_fs_sysfs_path(struct file *file, void __user *argp) * * When you add any new common ioctls to the switches above and below, * please ensure they have compatible arguments in compat mode. + * + * The LSM mailing list should also be notified of any command additions or + * changes, as specific LSMs may be affected. */ static int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd, unsigned long arg) From 5bf9e57e634bd72a97b4b12c87186fc052a6a116 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Thu, 25 Apr 2024 11:21:21 +0200 Subject: [PATCH 13/13] =?UTF-8?q?MAINTAINERS:=20Add=20G=C3=BCnther=20Noack?= =?UTF-8?q?=20as=20Landlock=20reviewer?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Günther is a major contributor to Landlock, both on the kernel and user space sides, and he is already reviewing Landlock changes. Thanks! Cc: James Morris Cc: Paul Moore Cc: Serge E. Hallyn Acked-by: Günther Noack Link: https://lore.kernel.org/r/20240425092126.975830-1-mic@digikod.net Signed-off-by: Mickaël Salaün --- MAINTAINERS | 1 + 1 file changed, 1 insertion(+) diff --git a/MAINTAINERS b/MAINTAINERS index b01345abadb2..4b261c8971c7 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12214,6 +12214,7 @@ F: net/l3mdev LANDLOCK SECURITY MODULE M: Mickaël Salaün +R: Günther Noack L: linux-security-module@vger.kernel.org S: Supported W: https://landlock.io