linux-stable.git/security, branch master

Merge tag 'landlock-7.0-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

2026-03-26T19:03:37+00:00

Pull Landlock fixes from Mickaël Salaün:
 "This mainly fixes Landlock TSYNC issues related to interrupts and
  unexpected task exit.

  Other fixes touch documentation and sample, and a new test extends
  coverage"

* tag 'landlock-7.0-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  landlock: Expand restrict flags example for ABI version 8
  selftests/landlock: Test tsync interruption and cancellation paths
  landlock: Clean up interrupted thread logic in TSYNC
  landlock: Serialize TSYNC thread restriction
  samples/landlock: Bump ABI version to 8
  landlock: Improve TSYNC types
  landlock: Fully release unused TSYNC work entries
  landlock: Fix formatting

xen/privcmd: add boot control for restricted usage in domU

2026-03-20T11:06:01+00:00

When running in an unprivileged domU under Xen, the privcmd driver
is restricted to allow only hypercalls against a target domain, for
which the current domU is acting as a device model.

Add a boot parameter "unrestricted" to allow all hypercalls (the
hypervisor will still refuse destructive hypercalls affecting other
guests).

Make this new parameter effective only in case the domU wasn't started
using secure boot, as otherwise hypercalls targeting the domU itself
might result in violating the secure boot functionality.

This is achieved by adding another lockdown reason, which can be
tested to not being set when applying the "unrestricted" option.

This is part of XSA-482

Signed-off-by: Juergen Gross 
---
V2:
- new patch

landlock: Clean up interrupted thread logic in TSYNC

2026-03-10T17:22:58+00:00

In landlock_restrict_sibling_threads(), when the calling thread is
interrupted while waiting for sibling threads to prepare, it executes
a recovery path.

Previously, this path included a wait_for_completion() call on
all_prepared to prevent a Use-After-Free of the local shared_ctx.
However, this wait is redundant. Exiting the main do-while loop
already leads to a bottom cleanup section that unconditionally waits
for all_finished. Therefore, replacing the wait with a simple break
is safe, prevents UAF, and correctly unblocks the remaining task_works.

Clean up the error path by breaking the loop and updating the
surrounding comments to accurately reflect the state machine.

Suggested-by: Günther Noack 
Signed-off-by: Yihan Ding 
Tested-by: Günther Noack 
Reviewed-by: Günther Noack 
Link: https://lore.kernel.org/r/20260306021651.744723-3-dingyihan@uniontech.com
Signed-off-by: Mickaël Salaün

landlock: Serialize TSYNC thread restriction

2026-03-10T17:22:56+00:00

syzbot found a deadlock in landlock_restrict_sibling_threads().
When multiple threads concurrently call landlock_restrict_self() with
sibling thread restriction enabled, they can deadlock by mutually
queueing task_works on each other and then blocking in kernel space
(waiting for the other to finish).

Fix this by serializing the TSYNC operations within the same process
using the exec_update_lock. This prevents concurrent invocations
from deadlocking.

We use down_write_trylock() and restart the syscall if the lock
cannot be acquired immediately. This ensures that if a thread fails
to get the lock, it will return to userspace, allowing it to process
any pending TSYNC task_works from the lock holder, and then
transparently restart the syscall.

Fixes: 42fc7e6543f6 ("landlock: Multithreading support for landlock_restrict_self()")
Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7ea2f5e9dfd468201817
Suggested-by: Günther Noack 
Suggested-by: Tingmao Wang 
Tested-by: Justin Suess 
Signed-off-by: Yihan Ding 
Tested-by: Günther Noack 
Reviewed-by: Günther Noack 
Link: https://lore.kernel.org/r/20260306021651.744723-2-dingyihan@uniontech.com
Signed-off-by: Mickaël Salaün

apparmor: fix race between freeing data and fs accessing it

2026-03-09T23:05:44+00:00

AppArmor was putting the reference to i_private data on its end after
removing the original entry from the file system. However the inode
can aand does live beyond that point and it is possible that some of
the fs call back functions will be invoked after the reference has
been put, which results in a race between freeing the data and
accessing it through the fs.

While the rawdata/loaddata is the most likely candidate to fail the
race, as it has the fewest references. If properly crafted it might be
possible to trigger a race for the other types stored in i_private.

Fix this by moving the put of i_private referenced data to the correct
place which is during inode eviction.

Fixes: c961ee5f21b20 ("apparmor: convert from securityfs to apparmorfs for policy ns files")
Reported-by: Qualys Security Advisory 
Reviewed-by: Georgia Garcia 
Reviewed-by: Maxime Bélair 
Reviewed-by: Cengiz Can 
Signed-off-by: John Johansen

apparmor: fix race on rawdata dereference

2026-03-09T23:05:44+00:00

There is a race condition that leads to a use-after-free situation:
because the rawdata inodes are not refcounted, an attacker can start
open()ing one of the rawdata files, and at the same time remove the
last reference to this rawdata (by removing the corresponding profile,
for example), which frees its struct aa_loaddata; as a result, when
seq_rawdata_open() is reached, i_private is a dangling pointer and
freed memory is accessed.

The rawdata inodes weren't refcounted to avoid a circular refcount and
were supposed to be held by the profile rawdata reference.  However
during profile removal there is a window where the vfs and profile
destruction race, resulting in the use after free.

Fix this by moving to a double refcount scheme. Where the profile
refcount on rawdata is used to break the circular dependency. Allowing
for freeing of the rawdata once all inode references to the rawdata
are put.

Fixes: 5d5182cae401 ("apparmor: move to per loaddata files, instead of replicating in profiles")
Reported-by: Qualys Security Advisory 
Reviewed-by: Georgia Garcia 
Reviewed-by: Maxime Bélair 
Reviewed-by: Cengiz Can 
Tested-by: Salvatore Bonaccorso 
Signed-off-by: John Johansen

apparmor: fix differential encoding verification

2026-03-09T23:05:43+00:00

Differential encoding allows loops to be created if it is abused. To
prevent this the unpack should verify that a diff-encode chain
terminates.

Unfortunately the differential encode verification had two bugs.

1. it conflated states that had gone through check and already been
   marked, with states that were currently being checked and marked.
   This means that loops in the current chain being verified are treated
   as a chain that has already been verified.

2. the order bailout on already checked states compared current chain
   check iterators j,k instead of using the outer loop iterator i.
   Meaning a step backwards in states in the current chain verification
   was being mistaken for moving to an already verified state.

Move to a double mark scheme where already verified states get a
different mark, than the current chain being kept. This enables us
to also drop the backwards verification check that was the cause of
the second error as any already verified state is already marked.

Fixes: 031dcc8f4e84 ("apparmor: dfa add support for state differential encoding")
Reported-by: Qualys Security Advisory 
Tested-by: Salvatore Bonaccorso 
Reviewed-by: Georgia Garcia 
Reviewed-by: Cengiz Can 
Signed-off-by: John Johansen

apparmor: fix unprivileged local user can do privileged policy management

2026-03-09T23:05:43+00:00

An unprivileged local user can load, replace, and remove profiles by
opening the apparmorfs interfaces, via a confused deputy attack, by
passing the opened fd to a privileged process, and getting the
privileged process to write to the interface.

This does require a privileged target that can be manipulated to do
the write for the unprivileged process, but once such access is
achieved full policy management is possible and all the possible
implications that implies: removing confinement, DoS of system or
target applications by denying all execution, by-passing the
unprivileged user namespace restriction, to exploiting kernel bugs for
a local privilege escalation.

The policy management interface can not have its permissions simply
changed from 0666 to 0600 because non-root processes need to be able
to load policy to different policy namespaces.

Instead ensure the task writing the interface has privileges that
are a subset of the task that opened the interface. This is already
done via policy for confined processes, but unconfined can delegate
access to the opened fd, by-passing the usual policy check.

Fixes: b7fd2c0340eac ("apparmor: add per policy ns .load, .replace, .remove interface files")
Reported-by: Qualys Security Advisory 
Tested-by: Salvatore Bonaccorso 
Reviewed-by: Georgia Garcia 
Reviewed-by: Cengiz Can 
Signed-off-by: John Johansen

apparmor: Fix double free of ns_name in aa_replace_profiles()

2026-03-09T23:05:43+00:00

if ns_name is NULL after
1071         error = aa_unpack(udata, &lh, &ns_name);

and if ent->ns_name contains an ns_name in
1089                 } else if (ent->ns_name) {

then ns_name is assigned the ent->ns_name
1095                         ns_name = ent->ns_name;

however ent->ns_name is freed at
1262                 aa_load_ent_free(ent);

and then again when freeing ns_name at
1270         kfree(ns_name);

Fix this by NULLing out ent->ns_name after it is transferred to ns_name

Fixes: 145a0ef21c8e9 ("apparmor: fix blob compression when ns is forced on a policy load
")
Reported-by: Qualys Security Advisory 
Tested-by: Salvatore Bonaccorso 
Reviewed-by: Georgia Garcia 
Reviewed-by: Cengiz Can 
Signed-off-by: John Johansen

apparmor: fix missing bounds check on DEFAULT table in verify_dfa()

2026-03-09T23:05:43+00:00

The verify_dfa() function only checks DEFAULT_TABLE bounds when the state
is not differentially encoded.

When the verification loop traverses the differential encoding chain,
it reads k = DEFAULT_TABLE[j] and uses k as an array index without
validation. A malformed DFA with DEFAULT_TABLE[j] >= state_count,
therefore, causes both out-of-bounds reads and writes.

[   57.179855] ==================================================================
[   57.180549] BUG: KASAN: slab-out-of-bounds in verify_dfa+0x59a/0x660
[   57.180904] Read of size 4 at addr ffff888100eadec4 by task su/993

[   57.181554] CPU: 1 UID: 0 PID: 993 Comm: su Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)
[   57.181558] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   57.181563] Call Trace:
[   57.181572]  
[   57.181577]  dump_stack_lvl+0x5e/0x80
[   57.181596]  print_report+0xc8/0x270
[   57.181605]  ? verify_dfa+0x59a/0x660
[   57.181608]  kasan_report+0x118/0x150
[   57.181620]  ? verify_dfa+0x59a/0x660
[   57.181623]  verify_dfa+0x59a/0x660
[   57.181627]  aa_dfa_unpack+0x1610/0x1740
[   57.181629]  ? __kmalloc_cache_noprof+0x1d0/0x470
[   57.181640]  unpack_pdb+0x86d/0x46b0
[   57.181647]  ? srso_alias_return_thunk+0x5/0xfbef5
[   57.181653]  ? srso_alias_return_thunk+0x5/0xfbef5
[   57.181656]  ? aa_unpack_nameX+0x1a8/0x300
[   57.181659]  aa_unpack+0x20b0/0x4c30
[   57.181662]  ? srso_alias_return_thunk+0x5/0xfbef5
[   57.181664]  ? stack_depot_save_flags+0x33/0x700
[   57.181681]  ? kasan_save_track+0x4f/0x80
[   57.181683]  ? kasan_save_track+0x3e/0x80
[   57.181686]  ? __kasan_kmalloc+0x93/0xb0
[   57.181688]  ? __kvmalloc_node_noprof+0x44a/0x780
[   57.181693]  ? aa_simple_write_to_buffer+0x54/0x130
[   57.181697]  ? policy_update+0x154/0x330
[   57.181704]  aa_replace_profiles+0x15a/0x1dd0
[   57.181707]  ? srso_alias_return_thunk+0x5/0xfbef5
[   57.181710]  ? __kvmalloc_node_noprof+0x44a/0x780
[   57.181712]  ? aa_loaddata_alloc+0x77/0x140
[   57.181715]  ? srso_alias_return_thunk+0x5/0xfbef5
[   57.181717]  ? _copy_from_user+0x2a/0x70
[   57.181730]  policy_update+0x17a/0x330
[   57.181733]  profile_replace+0x153/0x1a0
[   57.181735]  ? rw_verify_area+0x93/0x2d0
[   57.181740]  vfs_write+0x235/0xab0
[   57.181745]  ksys_write+0xb0/0x170
[   57.181748]  do_syscall_64+0x8e/0x660
[   57.181762]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[   57.181765] RIP: 0033:0x7f6192792eb2

Remove the MATCH_FLAG_DIFF_ENCODE condition to validate all DEFAULT_TABLE
entries unconditionally.

Fixes: 031dcc8f4e84 ("apparmor: dfa add support for state differential encoding")
Reported-by: Qualys Security Advisory 
Tested-by: Salvatore Bonaccorso 
Reviewed-by: Georgia Garcia 
Reviewed-by: Cengiz Can 
Signed-off-by: Massimiliano Pellizzer 
Signed-off-by: John Johansen