linux.git/security/landlock/fs.c, branch for-next Linux kernel source tree landlock: Refactor filesystem access mask management 2024-11-09T18:52:10+00:00 Mickaël Salaün mic@digikod.net 2024-11-09T11:08:54+00:00 0c0effb07f7d662af3e6f74da4d34241e412029b Replace get_raw_handled_fs_accesses() with a generic landlock_union_access_masks(), and replace get_fs_domain() with a generic landlock_get_applicable_domain(). These helpers will also be useful for other types of access. Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com> Reviewed-by: Günther Noack <gnoack@google.com> Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net [mic: Slightly improve doc as suggested by Günther] Signed-off-by: Mickaël Salaün <mic@digikod.net> 
Replace get_raw_handled_fs_accesses() with a generic
landlock_union_access_masks(), and replace get_fs_domain() with a
generic landlock_get_applicable_domain().  These helpers will also be
useful for other types of access.

Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net
[mic: Slightly improve doc as suggested by Günther]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
landlock: Add signal scoping 2024-09-16T21:50:52+00:00 Tahera Fahimi fahimitahera@gmail.com 2024-09-06T21:30:03+00:00 54a6e6bbf3bef25c8eb65619edde70af49bd3db0 Currently, a sandbox process is not restricted to sending a signal (e.g. SIGKILL) to a process outside the sandbox environment. The ability to send a signal for a sandboxed process should be scoped the same way abstract UNIX sockets are scoped. Therefore, we extend the "scoped" field in a ruleset with LANDLOCK_SCOPE_SIGNAL to specify that a ruleset will deny sending any signal from within a sandbox process to its parent (i.e. any parent sandbox or non-sandboxed processes). This patch adds file_set_fowner and file_free_security hooks to set and release a pointer to the file owner's domain. This pointer, fown_domain in landlock_file_security will be used in file_send_sigiotask to check if the process can send a signal. The ruleset_with_unknown_scope test is updated to support LANDLOCK_SCOPE_SIGNAL. This depends on two new changes: - commit 1934b212615d ("file: reclaim 24 bytes from f_owner"): replace container_of(fown, struct file, f_owner) with fown->file . - commit 26f204380a3c ("fs: Fix file_set_fowner LSM hook inconsistencies"): lock before calling the hook. Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> Closes: https://github.com/landlock-lsm/linux/issues/8 Link: https://lore.kernel.org/r/df2b4f880a2ed3042992689a793ea0951f6798a5.1725657727.git.fahimitahera@gmail.com [mic: Update landlock_get_current_domain()'s return type, improve and fix locking in hook_file_set_fowner(), simplify and fix sleepable call and locking issue in hook_file_send_sigiotask() and rebase on the latest VFS tree, simplify hook_task_kill() and quickly return when not sandboxed, improve comments, rename LANDLOCK_SCOPED_SIGNAL] Co-developed-by: Mickaël Salaün <mic@digikod.net> Signed-off-by: Mickaël Salaün <mic@digikod.net> 
Currently, a sandbox process is not restricted to sending a signal (e.g.
SIGKILL) to a process outside the sandbox environment.  The ability to
send a signal for a sandboxed process should be scoped the same way
abstract UNIX sockets are scoped. Therefore, we extend the "scoped"
field in a ruleset with LANDLOCK_SCOPE_SIGNAL to specify that a ruleset
will deny sending any signal from within a sandbox process to its parent
(i.e. any parent sandbox or non-sandboxed processes).

This patch adds file_set_fowner and file_free_security hooks to set and
release a pointer to the file owner's domain. This pointer, fown_domain
in landlock_file_security will be used in file_send_sigiotask to check
if the process can send a signal.

The ruleset_with_unknown_scope test is updated to support
LANDLOCK_SCOPE_SIGNAL.

This depends on two new changes:
- commit 1934b212615d ("file: reclaim 24 bytes from f_owner"): replace
  container_of(fown, struct file, f_owner) with fown->file .
- commit 26f204380a3c ("fs: Fix file_set_fowner LSM hook
  inconsistencies"): lock before calling the hook.

Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Closes: https://github.com/landlock-lsm/linux/issues/8
Link: https://lore.kernel.org/r/df2b4f880a2ed3042992689a793ea0951f6798a5.1725657727.git.fahimitahera@gmail.com
[mic: Update landlock_get_current_domain()'s return type, improve and
fix locking in hook_file_set_fowner(), simplify and fix sleepable call
and locking issue in hook_file_send_sigiotask() and rebase on the latest
VFS tree, simplify hook_task_kill() and quickly return when not
sandboxed, improve comments, rename LANDLOCK_SCOPED_SIGNAL]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
lsm: add the inode_free_security_rcu() LSM implementation hook 2024-08-12T19:35:04+00:00 Paul Moore paul@paul-moore.com 2024-07-09T23:43:06+00:00 63dff3e48871b0583be5032ff8fb7260c349a18c The LSM framework has an existing inode_free_security() hook which is used by LSMs that manage state associated with an inode, but due to the use of RCU to protect the inode, special care must be taken to ensure that the LSMs do not fully release the inode state until it is safe from a RCU perspective. This patch implements a new inode_free_security_rcu() implementation hook which is called when it is safe to free the LSM's internal inode state. Unfortunately, this new hook does not have access to the inode itself as it may already be released, so the existing inode_free_security() hook is retained for those LSMs which require access to the inode. Cc: stable@vger.kernel.org Reported-by: syzbot+5446fbf332b0602ede0b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000076ba3b0617f65cc8@google.com Signed-off-by: Paul Moore <paul@paul-moore.com> 
The LSM framework has an existing inode_free_security() hook which
is used by LSMs that manage state associated with an inode, but
due to the use of RCU to protect the inode, special care must be
taken to ensure that the LSMs do not fully release the inode state
until it is safe from a RCU perspective.

This patch implements a new inode_free_security_rcu() implementation
hook which is called when it is safe to free the LSM's internal inode
state.  Unfortunately, this new hook does not have access to the inode
itself as it may already be released, so the existing
inode_free_security() hook is retained for those LSMs which require
access to the inode.

Cc: stable@vger.kernel.org
Reported-by: syzbot+5446fbf332b0602ede0b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/00000000000076ba3b0617f65cc8@google.com
Signed-off-by: Paul Moore <paul@paul-moore.com>
landlock: Fix d_parent walk 2024-05-31T14:41:52+00:00 Mickaël Salaün mic@digikod.net 2024-05-16T18:19:34+00:00 88da52ccd66e65f2e63a6c35c9dff55d448ef4dc The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when trying to link a root mount point. This cannot work in practice because this directory is mounted, but the VFS check is done after the call to security_path_link(). Do not use source directory's d_parent when the source directory is the mount point. Cc: Günther Noack <gnoack@google.com> Cc: Paul Moore <paul@paul-moore.com> Cc: stable@vger.kernel.org Reported-by: syzbot+bf4903dc7e12b18ebc87@syzkaller.appspotmail.com Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER") Closes: https://lore.kernel.org/r/000000000000553d3f0618198200@google.com Link: https://lore.kernel.org/r/20240516181935.1645983-2-mic@digikod.net [mic: Fix commit message] Signed-off-by: Mickaël Salaün <mic@digikod.net> 
The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when
trying to link a root mount point.  This cannot work in practice because
this directory is mounted, but the VFS check is done after the call to
security_path_link().

Do not use source directory's d_parent when the source directory is the
mount point.

Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Reported-by: syzbot+bf4903dc7e12b18ebc87@syzkaller.appspotmail.com
Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Closes: https://lore.kernel.org/r/000000000000553d3f0618198200@google.com
Link: https://lore.kernel.org/r/20240516181935.1645983-2-mic@digikod.net
[mic: Fix commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
landlock: Add IOCTL access right for character and block devices 2024-05-13T04:58:29+00:00 Günther Noack gnoack@google.com 2024-04-19T16:11:12+00:00 b25f7415eb4108aa32dd3e74289d7f997090708f 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 <paul@paul-moore.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Günther Noack <gnoack@google.com> Link: https://lore.kernel.org/r/20240419161122.2023765-2-gnoack@google.com Signed-off-by: Mickaël Salaün <mic@digikod.net> 
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 <paul@paul-moore.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-2-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
landlock: Use f_cred in security_file_open() hook 2024-03-08T17:22:16+00:00 Mickaël Salaün mic@digikod.net 2024-03-07T09:52:03+00:00 63817febd1f3c27f633b2bce0d6db328e59fd019 Use landlock_cred(file->f_cred)->domain instead of landlock_get_current_domain() in security_file_open() hook implementation. This should not change the current behavior but could avoid potential race conditions in case of current task's credentials change. This will also ensure consistency with upcoming audit support relying on file->f_cred. Add and use a new get_fs_domain() helper to mask non-filesystem domains. file->f_cred is set by path_openat()/alloc_empty_file()/init_file() just before calling security_file_alloc(). Cc: Christian Brauner <brauner@kernel.org> Cc: Günther Noack <gnoack@google.com> Cc: Jann Horn <jannh@google.com> Cc: Paul Moore <paul@paul-moore.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20240307095203.1467189-1-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net> 
Use landlock_cred(file->f_cred)->domain instead of
landlock_get_current_domain() in security_file_open() hook
implementation.

This should not change the current behavior but could avoid potential
race conditions in case of current task's credentials change.

This will also ensure consistency with upcoming audit support relying on
file->f_cred.

Add and use a new get_fs_domain() helper to mask non-filesystem domains.

file->f_cred is set by path_openat()/alloc_empty_file()/init_file() just
before calling security_file_alloc().

Cc: Christian Brauner <brauner@kernel.org>
Cc: Günther Noack <gnoack@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240307095203.1467189-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
landlock: Add support for KUnit tests 2024-02-27T10:21:45+00:00 Mickaël Salaün mic@digikod.net 2024-01-18T11:36:32+00:00 b4007fd27206c478a4b76e299bddf4a71787f520 Add the SECURITY_LANDLOCK_KUNIT_TEST option to enable KUnit tests for Landlock. The minimal required configuration is listed in the security/landlock/.kunitconfig file. Add an initial landlock_fs KUnit test suite with 7 test cases for filesystem helpers. These are related to the LANDLOCK_ACCESS_FS_REFER right. There is one KUnit test case per: * mutated state (e.g. test_scope_to_request_*) or, * shared state between tests (e.g. test_is_eaccess_*). Add macros to improve readability of tests (i.e. one per line). Test cases are collocated with the tested functions to help maintenance and improve documentation. This is why SECURITY_LANDLOCK_KUNIT_TEST cannot be set as module. This is a nice complement to Landlock's user space kselftests. We expect new Landlock features to come with KUnit tests as well. Thanks to UML support, we can run all KUnit tests for Landlock with: ./tools/testing/kunit/kunit.py run --kunitconfig security/landlock [00:00:00] ======================= landlock_fs ======================= [00:00:00] [PASSED] test_no_more_access [00:00:00] [PASSED] test_scope_to_request_with_exec_none [00:00:00] [PASSED] test_scope_to_request_with_exec_some [00:00:00] [PASSED] test_scope_to_request_without_access [00:00:00] [PASSED] test_is_eacces_with_none [00:00:00] [PASSED] test_is_eacces_with_refer [00:00:00] [PASSED] test_is_eacces_with_write [00:00:00] =================== [PASSED] landlock_fs =================== [00:00:00] ============================================================ [00:00:00] Testing complete. Ran 7 tests: passed: 7 Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com> Reviewed-by: Günther Noack <gnoack@google.com> Link: https://lore.kernel.org/r/20240118113632.1948478-1-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net> 
Add the SECURITY_LANDLOCK_KUNIT_TEST option to enable KUnit tests for
Landlock.  The minimal required configuration is listed in the
security/landlock/.kunitconfig file.

Add an initial landlock_fs KUnit test suite with 7 test cases for
filesystem helpers.  These are related to the LANDLOCK_ACCESS_FS_REFER
right.

There is one KUnit test case per:
* mutated state (e.g. test_scope_to_request_*) or,
* shared state between tests (e.g. test_is_eaccess_*).

Add macros to improve readability of tests (i.e. one per line).  Test
cases are collocated with the tested functions to help maintenance and
improve documentation.  This is why SECURITY_LANDLOCK_KUNIT_TEST cannot
be set as module.

This is a nice complement to Landlock's user space kselftests.  We
expect new Landlock features to come with KUnit tests as well.

Thanks to UML support, we can run all KUnit tests for Landlock with:
./tools/testing/kunit/kunit.py run --kunitconfig security/landlock

[00:00:00] ======================= landlock_fs  =======================
[00:00:00] [PASSED] test_no_more_access
[00:00:00] [PASSED] test_scope_to_request_with_exec_none
[00:00:00] [PASSED] test_scope_to_request_with_exec_some
[00:00:00] [PASSED] test_scope_to_request_without_access
[00:00:00] [PASSED] test_is_eacces_with_none
[00:00:00] [PASSED] test_is_eacces_with_refer
[00:00:00] [PASSED] test_is_eacces_with_write
[00:00:00] =================== [PASSED] landlock_fs ===================
[00:00:00] ============================================================
[00:00:00] Testing complete. Ran 7 tests: passed: 7

Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240118113632.1948478-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
landlock: Fix asymmetric private inodes referring 2024-02-26T17:23:53+00:00 Mickaël Salaün mic@digikod.net 2024-02-19T19:03:45+00:00 d9818b3e906a0ee1ab02ea79e74a2f755fc5461a When linking or renaming a file, if only one of the source or destination directory is backed by an S_PRIVATE inode, then the related set of layer masks would be used as uninitialized by is_access_to_paths_allowed(). This would result to indeterministic access for one side instead of always being allowed. This bug could only be triggered with a mounted filesystem containing both S_PRIVATE and !S_PRIVATE inodes, which doesn't seem possible. The collect_domain_accesses() calls return early if is_nouser_or_private() returns false, which means that the directory's superblock has SB_NOUSER or its inode has S_PRIVATE. Because rename or link actions are only allowed on the same mounted filesystem, the superblock is always the same for both source and destination directories. However, it might be possible in theory to have an S_PRIVATE parent source inode with an !S_PRIVATE parent destination inode, or vice versa. To make sure this case is not an issue, explicitly initialized both set of layer masks to 0, which means to allow all actions on the related side. If at least on side has !S_PRIVATE, then collect_domain_accesses() and is_access_to_paths_allowed() check for the required access rights. Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christian Brauner <brauner@kernel.org> Cc: Günther Noack <gnoack@google.com> Cc: Jann Horn <jannh@google.com> Cc: Shervin Oloumi <enlightened@chromium.org> Cc: stable@vger.kernel.org Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER") Link: https://lore.kernel.org/r/20240219190345.2928627-1-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net> 
When linking or renaming a file, if only one of the source or
destination directory is backed by an S_PRIVATE inode, then the related
set of layer masks would be used as uninitialized by
is_access_to_paths_allowed().  This would result to indeterministic
access for one side instead of always being allowed.

This bug could only be triggered with a mounted filesystem containing
both S_PRIVATE and !S_PRIVATE inodes, which doesn't seem possible.

The collect_domain_accesses() calls return early if
is_nouser_or_private() returns false, which means that the directory's
superblock has SB_NOUSER or its inode has S_PRIVATE.  Because rename or
link actions are only allowed on the same mounted filesystem, the
superblock is always the same for both source and destination
directories.  However, it might be possible in theory to have an
S_PRIVATE parent source inode with an !S_PRIVATE parent destination
inode, or vice versa.

To make sure this case is not an issue, explicitly initialized both set
of layer masks to 0, which means to allow all actions on the related
side.  If at least on side has !S_PRIVATE, then
collect_domain_accesses() and is_access_to_paths_allowed() check for the
required access rights.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Günther Noack <gnoack@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Shervin Oloumi <enlightened@chromium.org>
Cc: stable@vger.kernel.org
Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Link: https://lore.kernel.org/r/20240219190345.2928627-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Merge tag 'landlock-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux 2024-01-09T21:22:15+00:00 Linus Torvalds torvalds@linux-foundation.org 2024-01-09T21:22:15+00:00 e9b4c5890858015bfe2089b7573319bcf4a92907 Pull Landlock updates from Mickaël Salaün: "New tests, a slight optimization, and some cosmetic changes" * tag 'landlock-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: landlock: Optimize the number of calls to get_access_mask slightly selftests/landlock: Rename "permitted" to "allowed" in ftruncate tests landlock: Remove remaining "inline" modifiers in .c files [v6.6] landlock: Remove remaining "inline" modifiers in .c files [v6.1] landlock: Remove remaining "inline" modifiers in .c files [v5.15] selftests/landlock: Add tests to check unhandled rule's access rights selftests/landlock: Add tests to check unknown rule's access rights 
Pull Landlock updates from Mickaël Salaün:
 "New tests, a slight optimization, and some cosmetic changes"

* tag 'landlock-6.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  landlock: Optimize the number of calls to get_access_mask slightly
  selftests/landlock: Rename "permitted" to "allowed" in ftruncate tests
  landlock: Remove remaining "inline" modifiers in .c files [v6.6]
  landlock: Remove remaining "inline" modifiers in .c files [v6.1]
  landlock: Remove remaining "inline" modifiers in .c files [v5.15]
  selftests/landlock: Add tests to check unhandled rule's access rights
  selftests/landlock: Add tests to check unknown rule's access rights
landlock: Remove remaining "inline" modifiers in .c files [v6.6] 2024-01-03T11:07:57+00:00 Günther Noack gnoack@google.com 2023-12-08T15:51:13+00:00 3406ebade1a84d1cdb0c342e1506b97a579d3834 For module-internal static functions, compilers are already in a good position to decide whether to inline them or not. Suggested-by: Mickaël Salaün <mic@digikod.net> Signed-off-by: Günther Noack <gnoack@google.com> Link: https://lore.kernel.org/r/20231208155121.1943775-2-gnoack@google.com [mic: Split patch for Linux 6.6] Signed-off-by: Mickaël Salaün <mic@digikod.net> 
For module-internal static functions, compilers are already in a good
position to decide whether to inline them or not.

Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20231208155121.1943775-2-gnoack@google.com
[mic: Split patch for Linux 6.6]
Signed-off-by: Mickaël Salaün <mic@digikod.net>