linux-stable.git/security/apparmor, branch master

apparmor: policy_int make sure list heads are initialized before fail path

2026-08-26T07:03:13+00:00

If profile create fails before policy_init is complete the list heads
are not properly initialized causing profile_free() sanity checks to
trigger the following splat.

AppArmor WARN aa_policy_destroy: (((!list_empty(&policy->profiles) && (&policy->profiles)->prev != ((void *) 0x122 + (0xdead000000000000UL))))):
WARNING: security/apparmor/lib.c:509 at aa_policy_destroy+0x164/0x1b0 security/apparmor/lib.c:509, CPU#0: syz.0.17/5541
Modules linked in:
CPU: 0 UID: 0 PID: 5541 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:aa_policy_destroy+0x16b/0x1b0 security/apparmor/lib.c:509
Code: 85 ed 7e 4d e8 96 bc 37 fd 5b 41 5c 41 5e 41 5f 5d e9 19 27 4e 07 cc e8 83 bc 37 fd 48 8d 3d 0c f0 d3 0b 48 c7 c6 a4 eb 38 8e <67> 48 0f b9 3a e9 04 ff ff ff e8 66 bc 37 fd 48 8d 3d ff ef d3 0b
RSP: 0018:ffffc9000345eaa0 EFLAGS: 00010293
RAX: ffffffff848f530d RBX: ffff88803f734800 RCX: ffff88801af2a580
RDX: 0000000000000000 RSI: ffffffff8e38eba4 RDI: ffffffff90634320
RBP: 0000000000000000 R08: 0000000000000cc0 R09: 00000000ffffffff
R10: dffffc0000000000 R11: fffffbfff1d95913 R12: dead000000000122
R13: ffff88803f734800 R14: ffff88803f734828 R15: dffffc0000000000
FS:  00007f5f6a1836c0(0000) GS:ffff88808c519000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d02407b048 CR3: 0000000012aa9000 CR4: 0000000000352ef0
Call Trace:
 
 aa_free_profile+0x9d/0x9f0 security/apparmor/policy.c:334
 aa_alloc_profile+0x1e4/0x3e0 security/apparmor/policy.c:416
 unpack_profile security/apparmor/policy_unpack.c:1153 [inline]
 aa_unpack+0x17db/0x7430 security/apparmor/policy_unpack.c:1748
 aa_replace_profiles+0x226/0x2a20 security/apparmor/policy.c:1183
 policy_update+0x234/0x4a0 security/apparmor/apparmorfs.c:505
 profile_load+0x1cb/0x320 security/apparmor/apparmorfs.c:522
 vfs_write+0x296/0xba0 fs/read_write.c:685
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5f6939e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5f6a183028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5f69625fa0 RCX: 00007f5f6939e0d9
RDX: 0000000000000041 RSI: 0000200000000400 RDI: 0000000000000003
RBP: 00007f5f6a183090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007f5f69626038 R14: 00007f5f69625fa0 R15: 00007ffe23725c18

Reported-by: syzbot+faed97c4ed43bfe7fee5@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=faed97c4ed43bfe7fee5
Fixes: fe6bb31f590c9 ("apparmor: split out shared policy_XXX fns to lib")
Signed-off-by: John Johansen

apparmor: fix deadlock in complain-mode change_hat

2026-08-16T06:39:38+00:00

The use of change_hat when in complain mode can cause a deadlock
when the hat doesn't exist and a new learning profile is created
for the missing profile. This is because change_hat() has taken
the lock to search the hat list and creating the new learning
profile needs to take the lock to add it to the list.

From the bug report:

Originally found in 7.0.0 in LTS ubuntu 26.04 with pam_apparmor + su
in complain mode set to change hats. Then verified in newest
available vanilla kernel I've compiled to see if still present:

7.2-rc7 vanilla -> affected

checked also some other kernels:
6.18.44 vanilla -> affected
6.12.95 with debian patches -> unaffected

On systems without bug (for example 6.12.95 debian) it just prints:

aa_change_hat rc=0

On systems with bug, the executable always hangs, prints nothing and
becomes unkillable. (And once stuck this way, it will cause any
further hat changes to also cause the changing process to get stuck)

Then in syslog you can find hint about cause:

kernel: INFO: task hat:3409 blocked for more than 483 seconds.
kernel: Not tainted 7.2.0-rc7 #1
kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: task:hat state:D stack:0 pid:3409 tgid:3409 ppid:2605 task_flags:0x400000 flags:0x00080800
kernel: Call Trace:
kernel:
kernel: __schedule+0x48f/0xfe0
kernel: schedule+0x27/0xa0
kernel: schedule_preempt_disabled+0x15/0x30
kernel: __mutex_lock.constprop.0+0x569/0xa10
kernel: aa_new_learning_profile+0x15f/0x210
kernel: build_change_hat+0x19f/0x3b0
kernel: change_hat.isra.0+0x5dd/0xd60
kernel: aa_change_hat+0x2f3/0x710
kernel: aa_setprocattr_changehat+0x121/0x1f0
kernel: do_setattr+0x28c/0x340
kernel: apparmor_setselfattr+0x20/0x50
kernel: security_setselfattr+0xf6/0x110
kernel: __x64_sys_lsm_set_self_attr+0x53/0x90
kernel: do_syscall_64+0xdd/0x5e0
kernel: ? __mod_memcg_lruvec_state+0xfd/0x260
kernel: ? lruvec_stat_mod_folio+0x8d/0xd0
kernel: ? __folio_mod_stat+0x2d/0x90
kernel: ? map_anon_folio_pte_nopf+0xd1/0x1f0
kernel: ? do_anonymous_page+0x184/0xa10
kernel: ? __handle_mm_fault+0x805/0x870
kernel: ? count_memcg_events+0xef/0x230
kernel: ? handle_mm_fault+0x1f0/0x2f0
kernel: ? do_user_addr_fault+0x2bb/0x7b0
kernel: ? do_syscall_64+0x94/0x5e0
kernel: ? exc_page_fault+0x75/0x160
kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e
kernel: RIP: 0033:0x7f815e134c8d
kernel: RSP: 002b:00007fff6df94ea8 EFLAGS: 00000246 ORIG_RAX: 00000000000001cc
kernel: RAX: ffffffffffffffda RBX: 0000556d8c81d040 RCX: 00007f815e134c8d
kernel: RDX: 0000000000000046 RSI: 0000556d8c81d040 RDI: 0000000000000064
kernel: RBP: 00007fff6df94ef0 R08: 00007f815e212ac8 R09: 000000000000000c
kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 0000556d8c81d010
kernel: R13: 0000000000000026 R14: 0000000000000046 R15: 0000000000000064
kernel:
kernel: INFO: task hat:3409 is blocked on a mutex likely owned by task hat:3409.

To fix the issue, lift the locking out of the core of
aa_new_learning_profile(), introduce a wrapper function that takes the
lock where needed, and have build_change_hat() call the core function
that no longer takes the lock.

In addition fix 4 other issues introduced by commit
32e92764d6f8d ("apparmor: grab ns lock and refresh when looking up changehat child profiles")
- aa_get_profile_rcu() was replaced-by: aa_get_profile without the
accompanying rcu_dereference_protected()
- an extra aa_get_label(label) was introduced at the start of
change_hat() without an accompanying aa_put_label() causing a
reference count leak.
- a reference count leak was introduced in the label_is_stale(label)
case, where the newest profile would be leaked instead of the
label passed to the function.
- a potential UAF when the lookup walks up the tree with new_ns != ns
the new label reference is put, and then used for the next lookup.
The mutex_lock, will block replacement, and removal in the locked
ns. However there are two cases where putting the reference can
result in the label being freed even with the lock held.

1. the label does not have a list reference (possible for temporary
or special profiles) in which case the put can trigger the
cleanup.
2. the new label reference is in a different namespace, which does
not have a lock held on it. This extends case 1 to also include
replacement, and removal that could be occurring in the namespace
new is in.

Reported-by: Martin Petricek
Link: https://lists.ubuntu.com/archives/apparmor/2026-August/014907.html
Fixes: 32e92764d6f8d ("apparmor: grab ns lock and refresh when looking up changehat child profiles")
Signed-off-by: John Johansen

apparmor: constify aa_label parameters on read-only query helpers

2026-08-11T05:49:43+00:00

Several label helpers only read from their struct aa_label * arguments:
they compare labels, test subset relationships, or check the mediation
bitmask, all via direct field/index access. Mark those parameters
const struct aa_label * to document intent and let the compiler enforce
that the label is not modified.

The converted functions are:
  - label_mediates(), label_mediates_safe()
  - aa_label_cmp() (and its vec_cmp() helper)
  - __aa_label_next_not_in_set(), aa_label_is_subset(),
    aa_label_is_unconfined_subset()
  - __aa_subj_label_is_cached()
  - aa_label_next_confined(), aa_label_next_in_merge()

These all access the label through direct indexing or manual iterators
rather than the label_for_each()/fn_for_each() macros, which are not
const-correct and so gate the majority of the remaining label consumers
(the print, match, and permission-check paths) from being constified.

No functional change.

Signed-off-by: John Johansen 
Assisted-by: Claude:claude-opus-4.8

apparmor: constify aa_dfa parameters on read-only compute paths

2026-08-11T05:49:43+00:00

Most uses of aa_dfa a read-only walking of the dfa. Have the compiler
enforce this.

Signed-off-by: John Johansen

apparmor: constify aa_profile parameters on read-only compute paths

2026-08-11T05:49:43+00:00

A number of functions take a struct aa_profile * argument that is only
ever read from: they compute DFA matches or apply the profile's mode
flags without modifying the profile, taking a reference on it, or
touching its embedded label. Mark those parameters const struct
aa_profile * to document intent and let the compiler enforce it.

The converted functions are the permission "compute" path plus a few
pure readers:
  - aa_apply_modes_to_perms(), aa_profile_match_label()
  - AUDIT_MODE()
  - aa_label_match() and its match_component()/label_compound_match()/
    label_components_match() helpers (label.c)
  - match_component()/label_compound_match()/label_components_match()/
    label_match()/change_profile_perms()/aa_xattrs_match() (domain.c)
  - match_iface()/match_addr_iface()/match_addr_iface_label()/
    skb_match_to_sk()/skb_match_to_cmd() (af_inet.c)
  - aa_profile_capget(), path_flags(), profile_query_cb()

The remaining aa_profile * parameters cannot be made const: the audit
path stores &profile->label into the owned, refcounted
apparmor_audit_data.subj_label/peer fields, and the domain/lifecycle
paths take references on the profile's embedded label
(aa_get_label()/aa_get_newest_label()/aa_get_profile()) or write
profile fields.

No functional change.

Signed-off-by: John Johansen 
Assisted-by: Claude:claude-opus-4.8

apparmor: constify aa_perms parameters that are read-only

2026-08-11T05:49:42+00:00

Several functions take a struct aa_perms * argument that is only ever
read from and never modified through the pointer. Mark those parameters
const struct aa_perms * to document intent and let the compiler enforce
that the permission set is not mutated.

The converted functions are:
  - aa_check_perms()
  - aa_do_perms()
  - do_perms() (af_inet)
  - match_label() (af_unix)
  - verify_perm()
  - aa_perms_accum() / aa_perms_accum_raw() (@addend only)

No functional change.

Signed-off-by: John Johansen 
Assisted-by: Claude:claude-opus-4.8

apparmor: drop use of _confined variant for iteration

2026-08-11T05:49:42+00:00

In preparation for allowing unconfined to be replaced and mediate
select rules drop use of the _confined variant for iteration in
the mount code.

The RULE_MEDIATES() check will continue to allow unconfined profile
mediation to be skipped unless it is replaced and is given mount
rules.

Signed-off-by: John Johansen

apparmor: refactory mount to use check_perms

2026-08-11T05:49:42+00:00

Move the mount permissions check to use the common backend
aa_check_perms() to check permissions. This will make it so caching,
audit, complain, logic can be handled consistently in a single place.

Signed-off-by: John Johansen

apparmor: fix auditing of mount binary data

2026-08-11T05:49:42+00:00

AppArmor only mediates non-binary mount data, and should only
audit the mount data if it is non-binary.

Signed-off-by: John Johansen

apparmor: add audit mode to provide a mechanism to silence complain messages

2026-08-11T05:49:42+00:00

Complain messages can be very noisy and fill the logs quickly. Allow
complain (allow) messages to be silenced separate from denied
messages.

Signed-off-by: John Johansen