linux-stable.git/kernel, branch v6.6.148

locking/rt: Fix the incorrect RCU protection in rt_spin_unlock()

2026-08-03T09:15:39+00:00

[ Upstream commit 89038cc87d80c77e7aa6f42a64b2573b74af339f ]

rt_spin_unlock() releases the RCU protection before unlocking the
lock. That opens the door for the following UAF scenario:

 T1					T2
 spin_lock(&p->lock);		rcu_read_lock();
 invalidate(p);			p = rcu_dereference(ptr);
 rcu_assign_pointer(ptr, NULL);	if (!p) return;
 spin_unlock(&p->lock);		spin_lock(&p->lock)
 				   lock(&lock->lock);
				   rcu_read_lock();
 kfree_rcu(p);			rcu_read_unlock();
				....
				spin_unlock(&p->lock)
				  rcu_read_unlock(); // Ends grace period
 rcu_do_batch()
   kfree(p);
			    UAF ->	  rt_mutex_cmpxchg_release(&lock->lock...)

Regular spinlocks keep preemption disabled accross the unlock operation,
which provides full RCU protection, but the RT substitution fails to
resemble that. Same applies for the rwlock substitution.

Move the rcu_read_unlock() invocation past the unlock operations to match
the non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but
that's harmless as the caller needs to hold RCU read lock across the lock
operation. The migrate_enable() call stays before the unlock operation
because there is no per CPU operation in the unlock path which would
require migration to be kept disabled.

Fixes: 0f383b6dc96e ("locking/spinlock: Provide RT variant")
Reported-by: syzbot+000c800a02097aaa10ed@syzkaller.appspotmail.com
Decoded-by: Jann Horn 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Sebastian Andrzej Siewior 
Acked-by: Al Viro 
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/87jyrud75z.ffs@fw13
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

tracing/user_events: Fix use-after-free in user_event_mm_dup()

2026-08-03T09:15:38+00:00

[ Upstream commit 50fd6dd755c6e48a38af2fa4621167eea56829c2 ]

user_event_mm_dup() walks the parent mm's enabler list locklessly under
rcu_read_lock() during fork() (from copy_process()); it does not take
event_mutex:

	rcu_read_lock();
	list_for_each_entry_rcu(enabler, &old_mm->enablers, mm_enablers_link)
		enabler->event = user_event_get(orig->event);

user_event_enabler_destroy() removes an enabler from that list with
list_del_rcu() and then, without waiting for a grace period, drops the
enabler's user_event reference with user_event_put() and frees the enabler
with kfree(). A reader that loaded the enabler before the list_del_rcu()
can still be walking it, which leads to two use-after-frees:

 - kfree(enabler) frees the enabler while that reader dereferences
   enabler->event.

 - user_event_put() may drop the last reference to the user_event, which
   is then freed (via delayed_destroy_user_event() on a work queue), while
   the same reader does user_event_get(orig->event) on it.

Both are reachable by an unprivileged task that can open user_events_data:
one multithreaded process that registers an enabler and then concurrently
unregisters it and calls fork() triggers the race. KASAN reports a
slab-use-after-free in user_event_mm_dup() during clone(), with a
"refcount_t: addition on 0" warning when the user_event is freed.

The enabler use-after-free was found first; the user_event one was reported
by XIAO WU, and the earlier enabler-only fix did not address it.

Defer both the user_event_put() and the kfree(enabler) to a work item
queued with queue_rcu_work(), so they run only after an RCU grace period,
once all readers walking the enabler list have finished. The put must run
in process context because user_event_put() takes event_mutex on the last
reference, so a work queue is used rather than call_rcu(). The now-unlocked
put lets the locked argument of user_event_enabler_destroy() be removed;
all callers are updated.

Fixes: 7235759084a4 ("tracing/user_events: Use remote writes for event enablement")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260707165912.2560537-2-michael.bommarito@gmail.com
Reported-by: XIAO WU 
Closes: https://lore.kernel.org/all/tencent_89647CE40DC452B891C65C94D1B271DE8E07@qq.com/
Suggested-by: Beau Belgrave 
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito 
Signed-off-by: Steven Rostedt 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

workqueue: Add system_percpu_wq and system_dfl_wq

2026-08-03T09:15:38+00:00

[ Upstream commit 128ea9f6ccfb6960293ae4212f4f97165e42222d ]

Currently, if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users. Make it
clear by adding a system_percpu_wq.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

Suggested-by: Tejun Heo 
Signed-off-by: Marco Crivellari 
Signed-off-by: Tejun Heo 
Stable-dep-of: 50fd6dd755c6 ("tracing/user_events: Fix use-after-free in user_event_mm_dup()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

workqueue: Factor out init_cpu_worker_pool()

2026-08-03T09:15:38+00:00

[ Upstream commit 2fcdb1b44491e08f5334a92c50e8f362e0d46f91 ]

Factor out init_cpu_worker_pool() from workqueue_init_early(). This is pure
reorganization in preparation of BH workqueue support.

Signed-off-by: Tejun Heo 
Tested-by: Allen Pais 
Stable-dep-of: 50fd6dd755c6 ("tracing/user_events: Fix use-after-free in user_event_mm_dup()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

taskstats: retain dead thread stats in TGID queries

2026-08-03T09:15:37+00:00

[ Upstream commit b3e4fbb04220efc3bc022bcf31b5689d39c6b111 ]

Patch series "taskstats: fix TGID dead-thread stat retention", v3.

This series fixes a taskstats TGID aggregation bug where fields added in
the TGID query path were not preserved after thread exit, and adds a
kselftest covering the regression.

The first patch keeps the cached TGID aggregate used for dead threads in
step with the fields already accumulated for live threads, and also fixes
the final TGID exit notification emitted when group_dead is true.

The second patch adds a kselftest that verifies TGID CPU stats do not
regress after a worker thread exits and has been reaped.

This patch (of 2):

fill_stats_for_tgid() builds TGID stats from two sources: the cached
aggregate in signal->stats and a scan of the live threads in the group.

However, fill_tgid_exit() only accumulates delay accounting into
signal->stats.  This means that once a thread exits, TGID queries lose the
fields that fill_stats_for_tgid() adds for live threads.

This gap was introduced incrementally by two earlier changes that extended
fill_stats_for_tgid() but did not make the corresponding update to
fill_tgid_exit():

- commit 8c733420bdd5 ("taskstats: add e/u/stime for TGID command")
  added ac_etime, ac_utime, and ac_stime to the TGID query path.
- commit b663a79c1915 ("taskstats: add context-switch counters")
  added nvcsw and nivcsw to the TGID query path.

As a result, those fields were accounted for live threads in TGID queries,
but were dropped from the cached TGID aggregate after thread exit.  The
final TGID exit notification emitted when group_dead is true also copies
that cached aggregate, so it loses the same fields.

Factor the per-task TGID accumulation into tgid_stats_add_task() and use
it in both fill_stats_for_tgid() and fill_tgid_exit().  This keeps the
cached aggregate used for dead threads aligned with the live-thread
accumulation used by TGID queries.

Link: https://lore.kernel.org/cover.1776094300.git.cyyzero16@gmail.com
Link: https://lore.kernel.org/abd2a15d33343636ab5ba43d540bcfe508bd66c7.1776094300.git.cyyzero16@gmail.com
Fixes: 8c733420bdd5 ("taskstats: add e/u/stime for TGID command")
Fixes: b663a79c1915 ("taskstats: add context-switch counters")
Signed-off-by: Yiyang Chen 
Acked-by: Balbir Singh 
Cc: Dr. Thomas Orgis 
Cc: Oleg Nesterov 
Cc: Wang Yaxin 
Cc: Yang Yang 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

taskstats: fill_stats_for_tgid: use for_each_thread()

2026-08-03T09:15:37+00:00

[ Upstream commit ed5378a387fd7c382497f2abcf4605e030b64044 ]

do/while_each_thread should be avoided when possible.

Plus I _think_ this change allows to avoid lock_task_sighand() but I am
not sure, I forgot everything about taskstats.  In any case, this code
does not look right in that the same thread can be accounted twice:
taskstats_exit() can account the exiting thread in signal->stats and drop
->siglock but this thread is still on the thread-group list, so
lock_task_sighand() can't help.

Link: https://lkml.kernel.org/r/20230909214951.GA24274@redhat.com
Signed-off-by: Oleg Nesterov 
Cc: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Stable-dep-of: b3e4fbb04220 ("taskstats: retain dead thread stats in TGID queries")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

audit: fix recursive locking deadlock in audit_dupe_exe()

2026-08-03T09:15:34+00:00

[ Upstream commit 81905b5acbe77284734438df3fbec1158e6429a3 ]

A deadlock occurs in the audit subsystem when duplicating
executable-related rules.

When a file is moved (e.g., via do_renameat2()), the VFS layer locks
the parent directory (I_MUTEX_PARENT), which synchronously triggers an
fsnotify_move event. If an existing executable audit rule matches the
file being moved, the audit subsystem catches this event and calls
audit_dupe_exe() to duplicate the watch and update the rule. Then,
audit_alloc_mark() would call kern_path_parent() to resolve the path,
leading to a blind attempt to acquire the exact same I_MUTEX_PARENT lock
already held by the task, resulting in the following recursive locking
deadlock:

 ============================================
 WARNING: possible recursive locking detected
 6.12.0-55.27.1.el10_0.x86_64+debug #1 Not tainted
 --------------------------------------------
 mv/5099 is trying to acquire lock:
 ffff888132845358 (&inode->i_sb->s_type->i_mutex_dir_key/1){+.+.}-{3:3},
 at: __kern_path_locked+0x10a/0x2f0

 but task is already holding lock:
 ffff888132846b58 (&inode->i_sb->s_type->i_mutex_dir_key/1){+.+.}-{3:3},
 at: lock_two_directories+0x13f/0x2b0

 other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(&inode->i_sb->s_type->i_mutex_dir_key/1);
   lock(&inode->i_sb->s_type->i_mutex_dir_key/1);

  *** DEADLOCK ***

  May be due to missing lock nesting notation

  6 locks held by mv/5099:
  #0: ffff888112a9c440 (sb_writers#13)
  at: do_renameat2+0x34c/0xbc0
  #1: ffff888112a9c790 (&type->s_vfs_rename_key#3)
  at: do_renameat2+0x415/0xbc0
  #2: ffff888132846b58 (&inode->i_sb->s_type->i_mutex_dir_key/1)
  at: lock_two_directories+0x13f/0x2b0
  #3: ffff888132845358 (&inode->i_sb->s_type->i_mutex_dir_key/5)
  at: lock_two_directories+0x175/0x2b0
  #4: ffffffffb3a1fb10 (&fsnotify_mark_srcu)
  at: fsnotify+0x454/0x28a0
  #5: ffffffffaf886230 (audit_filter_mutex)
  at: audit_update_watch+0x36/0x11e0

 stack backtrace:
 Call Trace:
  
  dump_stack_lvl+0x6f/0xb0
  print_deadlock_bug.cold+0xbd/0xca
  validate_chain+0x83a/0xf00
  __lock_acquire+0xcac/0x1d20
  lock_acquire.part.0+0x11b/0x360
  down_write_nested+0x9f/0x230
  __kern_path_locked+0x10a/0x2f0
  kern_path_locked+0x26/0x40
  audit_alloc_mark+0xfb/0x4f0
  audit_dupe_exe+0x6c/0xe0
  audit_dupe_rule+0x6c2/0xc00
  audit_update_watch+0x4cc/0x11e0
  audit_watch_handle_event+0x12c/0x1b0
  send_to_group+0x5d0/0x8b0
  fsnotify+0x615/0x28a0
  fsnotify_move+0x1d8/0x630
  vfs_rename+0xdcd/0x1df0
  do_renameat2+0x9d4/0xbc0
  __x64_sys_renameat+0x192/0x260
  do_syscall_64+0x92/0x180
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7f0491fe8c4e
 Code: 0f 1f 40 00 48 8b 15 c1 e1 16 00 f7 d8 64 89 02 b8 ff ff ff ff
 c3 66 0f 1f 44 00 00 f3 0f 1e fa 49 89 ca b8 08 01 00 00 0f 05 <48>
 3d 00 f0 ff ff 77 0a c3 66 0f 1f 84 00 00 00 00 00 48 8b 15 89
 RSP: 002b:00007ffc7210bf38 EFLAGS: 00000246 ORIG_RAX: 0000000000000108
 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0491fe8c4e
 RDX: 0000000000000003 RSI: 00007ffc7210e6c8 RDI: 00000000ffffff9c
 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
 R10: 00005575eb2dae2a R11: 0000000000000246 R12: 00005575eb2dae2a
 R13: 00007ffc7210e6c8 R14: 0000000000000003 R15: 00000000ffffff9c
  

The aforementioned deadlock can be consistently reproduced by running
the script below:

 audit-dupe-exe-deadlock.sh
 --------------------------
 #!/bin/bash
 auditctl -D
 mkdir -p /tmp/foo
 touch /tmp/file
 auditctl -a always,exit -F exe=/tmp/file -F path=/tmp/file -S all -k dr
 mv /tmp/file /tmp/foo/file
 rm -Rf /tmp/foo

This patch fixes the issue by introducing struct audit_watch_ctx to pass
the fsnotify event context down to audit_alloc_mark(). By utilizing the
already-resolved directory inode provided by the event, we bypass the
kern_path_parent() path resolution entirely, safely avoiding the
recursive lock. Furthermore, it explicitly allows duplicate fsnotify
marks (allow_dups = 1) during the rename update, allowing the new rule's
mark to safely coexist with the old rule's mark until the old rule is
freed.

P.S.: This issue was identified and reproduced during a comprehensive
code coverage analysis of the audit subsystem. The full report is
available at the link below:

https://people.redhat.com/rrobaina/audit-code-coverage-analysis.pdf

P.P.S: With the permission of both Ricardo and Nathan, I've squashed a
fixup patch from Nathan that addresses a compile time error when
CONFIG_AUDITSYSCALL=n.

Cc: stable@kernel.org
Fixes: 34d99af52ad4 ("audit: implement audit by executable")
Acked-by: Waiman Long 
Acked-by: Richard Guy Briggs 
Signed-off-by: Nathan Chancellor 
Signed-off-by: Ricardo Robaina 
[PM: move link metadata into the msg, apply fix from NC]
Signed-off-by: Paul Moore 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

audit: use 'unsigned int' instead of 'unsigned'

2026-08-03T09:15:34+00:00

[ Upstream commit 8b226771014beab1292081151a99530886ce54b4 ]

Address checkpatch.pl warning below, across the audit subsystem:

  WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

Minor cleanup, no functional changes.

Signed-off-by: Ricardo Robaina 
Signed-off-by: Paul Moore 
Stable-dep-of: 81905b5acbe7 ("audit: fix recursive locking deadlock in audit_dupe_exe()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

audit: widen ino fields to u64

2026-08-03T09:15:33+00:00

[ Upstream commit 125dfa218134df7cc112667e92984de9d8cd0bf6 ]

inode->i_ino is being widened from unsigned long to u64. The audit
subsystem uses unsigned long ino in struct fields, function parameters,
and local variables that store inode numbers from arbitrary filesystems.
On 32-bit platforms this truncates inode numbers that exceed 32 bits,
which will cause incorrect audit log entries and broken watch/mark
comparisons.

Widen all audit ino fields, parameters, and locals to u64, and update
the inode format string from %lu to %llu to match.

Signed-off-by: Jeff Layton 
Link: https://patch.msgid.link/20260304-iino-u64-v3-2-2257ad83d372@kernel.org
Acked-by: Paul Moore 
Signed-off-by: Christian Brauner 
Stable-dep-of: 81905b5acbe7 ("audit: fix recursive locking deadlock in audit_dupe_exe()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

VFS/audit: introduce kern_path_parent() for audit

2026-08-03T09:15:33+00:00

[ Upstream commit 76a53de6f7ff0641570364234fb4489f4d4fc8e9 ]

audit_alloc_mark() and audit_get_nd() both need to perform a path
lookup getting the parent dentry (which must exist) and the final
target (following a LAST_NORM name) which sometimes doesn't need to
exist.

They don't need the parent to be locked, but use kern_path_locked() or
kern_path_locked_negative() anyway.  This is somewhat misleading to the
casual reader.

This patch introduces a more targeted function, kern_path_parent(),
which returns not holding locks.  On success the "path" will
be set to the parent, which must be found, and the return value is the
dentry of the target, which might be negative.

This will clear the way to rename kern_path_locked() which is
otherwise only used to prepare for removing something.

It also allows us to remove kern_path_locked_negative(), which is
transformed into the new kern_path_parent().

Signed-off-by: NeilBrown 
Signed-off-by: Christian Brauner 
Stable-dep-of: 81905b5acbe7 ("audit: fix recursive locking deadlock in audit_dupe_exe()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman