kernel/linux.git/security/landlock, branch v5.15.209

landlock: Add the errata interface

2025-05-02T05:44:20+00:00

commit 15383a0d63dbcd63dc7e8d9ec1bf3a0f7ebf64ac upstream. Some fixes may require user space to check if they are applied on the running kernel before using a specific feature. For instance, this applies when a restriction was previously too restrictive and is now getting relaxed (e.g. for compatibility reasons). However, non-visible changes for legitimate use (e.g. security fixes) do not require an erratum. Because fixes are backported down to a specific Landlock ABI, we need a way to avoid cherry-pick conflicts. The solution is to only update a file related to the lower ABI impacted by this issue. All the ABI files are then used to create a bitmask of fixes. The new errata interface is similar to the one used to get the supported Landlock ABI version, but it returns a bitmask instead because the order of fixes may not match the order of versions, and not all fixes may apply to all versions. The actual errata will come with dedicated commits. The description is not actually used in the code but serves as documentation. Create the landlock_abi_version symbol and use its value to check errata consistency. Update test_base's create_ruleset_checks_ordering tests and add errata tests. This commit is backportable down to the first version of Landlock. Fixes: 3532b0b4352c ("landlock: Enable user space to infer supported features") Cc: Günther Noack Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250318161443.279194-3-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Handle weird files

2025-03-13T11:49:58+00:00

[ Upstream commit 49440290a0935f428a1e43a5ac8dc275a647ff80 ] A corrupted filesystem (e.g. bcachefs) might return weird files. Instead of throwing a warning and allowing access to such file, treat them as regular files. Cc: Dave Chinner Cc: Kent Overstreet Cc: Paul Moore Reported-by: syzbot+34b68f850391452207df@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/000000000000a65b35061cffca61@google.com Reported-by: syzbot+360866a59e3c80510a62@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/67379b3f.050a0220.85a0.0001.GAE@google.com Reported-by: Ubisectech Sirius Closes: https://lore.kernel.org/r/c426821d-8380-46c4-a494-7008bbd7dd13.bugreport@ubisectech.com Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control") Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20250110153918.241810-1-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Sasha Levin

landlock: Move filesystem helpers and add a new one

2025-03-13T11:49:57+00:00

[ Upstream commit 9da82b20fde95814af721a2a7b1796a5b4a3d78e ] Move the SB_NOUSER and IS_PRIVATE dentry check to a standalone is_nouser_or_private() helper. This will be useful for a following commit. Move get_mode_access() and maybe_remove() to make them usable by new code provided by a following commit. Reviewed-by: Paul Moore Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220506161102.525323-6-mic@digikod.net Stable-dep-of: 49440290a093 ("landlock: Handle weird files") Signed-off-by: Sasha Levin

landlock: Don't lose track of restrictions on cred_transfer

2024-08-19T03:45:10+00:00

commit 39705a6c29f8a2b93cf5b99528a55366c50014d1 upstream. When a process' cred struct is replaced, this _almost_ always invokes the cred_prepare LSM hook; but in one special case (when KEYCTL_SESSION_TO_PARENT updates the parent's credentials), the cred_transfer LSM hook is used instead. Landlock only implements the cred_prepare hook, not cred_transfer, so KEYCTL_SESSION_TO_PARENT causes all information on Landlock restrictions to be lost. This basically means that a process with the ability to use the fork() and keyctl() syscalls can get rid of all Landlock restrictions on itself. Fix it by adding a cred_transfer hook that does the same thing as the existing cred_prepare hook. (Implemented by having hook_cred_prepare() call hook_cred_transfer() so that the two functions are less likely to accidentally diverge in the future.) Cc: stable@kernel.org Fixes: 385975dca53e ("landlock: Set up the security framework and manage credentials") Signed-off-by: Jann Horn Link: https://lore.kernel.org/r/20240724-landlock-houdini-fix-v1-1-df89a4560ca3@google.com Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Warn once if a Landlock action is requested while disabled

2024-04-10T14:18:39+00:00

[ Upstream commit 782191c74875cc33b50263e21d76080b1411884d ] Because sandboxing can be used as an opportunistic security measure, user space may not log unsupported features. Let the system administrator know if an application tries to use Landlock but failed because it isn't enabled at boot time. This may be caused by boot loader configurations with outdated "lsm" kernel's command-line parameter. Cc: stable@vger.kernel.org Fixes: 265885daf3e5 ("landlock: Add syscall implementations") Reviewed-by: Kees Cook Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20240227110550.3702236-2-mic@digikod.net Signed-off-by: Mickaël Salaün Signed-off-by: Sasha Levin

landlock: Fix same-layer rule unions

2022-06-09T08:23:24+00:00

commit 8ba0005ff418ec356e176b26eaa04a6ac755d05b upstream. The original behavior was to check if the full set of requested accesses was allowed by at least a rule of every relevant layer. This didn't take into account requests for multiple accesses and same-layer rules allowing the union of these accesses in a complementary way. As a result, multiple accesses requested on a file hierarchy matching rules that, together, allowed these accesses, but without a unique rule allowing all of them, was illegitimately denied. This case should be rare in practice and it can only be triggered by the path_rename or file_open hook implementations. For instance, if, for the same layer, a rule allows execution beneath /a/b and another rule allows read beneath /a, requesting access to read and execute at the same time for /a/b should be allowed for this layer. This was an inconsistency because the union of same-layer rule accesses was already allowed if requested once at a time anyway. This fix changes the way allowed accesses are gathered over a path walk. To take into account all these rule accesses, we store in a matrix all layer granting the set of requested accesses, according to the handled accesses. To avoid heap allocation, we use an array on the stack which is 2*13 bytes. A following commit bringing the LANDLOCK_ACCESS_FS_REFER access right will increase this size to reach 112 bytes (2*14*4) in case of link or rename actions. Add a new layout1.layer_rule_unions test to check that accesses from different rules pertaining to the same layer are ORed in a file hierarchy. Also test that it is not the case for rules from different layers. Reviewed-by: Paul Moore Link: https://lore.kernel.org/r/20220506161102.525323-5-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Create find_rule() from unmask_layers()

2022-06-09T08:23:24+00:00

commit 2cd7cd6eed88b8383cfddce589afe9c0ae1d19b4 upstream. This refactoring will be useful in a following commit. Reviewed-by: Paul Moore Link: https://lore.kernel.org/r/20220506161102.525323-4-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Reduce the maximum number of layers to 16

2022-06-09T08:23:24+00:00

commit 75c542d6c6cc48720376862d5496d51509160dfd upstream. The maximum number of nested Landlock domains is currently 64. Because of the following fix and to help reduce the stack size, let's reduce it to 16. This seems large enough for a lot of use cases (e.g. sandboxed init service, spawning a sandboxed SSH service, in nested sandboxed containers). Reducing the number of nested domains may also help to discover misuse of Landlock (e.g. creating a domain per rule). Add and use a dedicated layer_mask_t typedef to fit with the number of layers. This might be useful when changing it and to keep it consistent with the maximum number of layers. Reviewed-by: Paul Moore Link: https://lore.kernel.org/r/20220506161102.525323-3-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Define access_mask_t to enforce a consistent access mask size

2022-06-09T08:23:24+00:00

commit 5f2ff33e10843ef51275c8611bdb7b49537aba5d upstream. Create and use the access_mask_t typedef to enforce a consistent access mask size and uniformly use a 16-bits type. This will helps transition to a 32-bits value one day. Add a build check to make sure all (filesystem) access rights fit in. This will be extended with a following commit. Reviewed-by: Paul Moore Link: https://lore.kernel.org/r/20220506161102.525323-2-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman

landlock: Change landlock_restrict_self(2) check ordering

2022-06-09T08:23:24+00:00

commit eba39ca4b155c54adf471a69e91799cc1727873f upstream. According to the Landlock goal to be a security feature available to unprivileges processes, it makes more sense to first check for no_new_privs before checking anything else (i.e. syscall arguments). Merge inval_fd_enforce and unpriv_enforce_without_no_new_privs tests into the new restrict_self_checks_ordering. This is similar to the previous commit checking other syscalls. Link: https://lore.kernel.org/r/20220506160820.524344-10-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Signed-off-by: Greg Kroah-Hartman