mirror/android_kernel_fxtec_sm6115
3
0
Fork 0
mirror of https://github.com/LineageOS/android_kernel_fxtec_sm6115.git synced 2026-08-18 10:41:12 +00:00
Code Issues Packages Projects Releases Wiki Activity

BACKPORT: locking/rtmutex: Skip remove_waiter() when waiter is not enqueued

Browse Source 
syzbot triggered the following splat in remove_waiter() via
FUTEX_CMP_REQUEUE_PI:

  KASAN: null-ptr-deref in range [0x0000000000000a88-0x0000000000000a8f]
   class_raw_spinlock_constructor
   remove_waiter+0x159/0x1200 kernel/locking/rtmutex.c:1561
   rt_mutex_start_proxy_lock+0x103/0x120
   futex_requeue+0x10e4/0x20d0
   __x64_sys_futex+0x34f/0x4d0

task_blocks_on_rt_mutex() does not arm the waiter upon deadlock detection,
leaving waiter->task nil, where 3bfdc63936dd ("rtmutex: Use waiter::task instead
of current in remove_waiter()") made this fatal.

Furthermore, rt_mutex_start_proxy_lock() should not be calling into remove_waiter()
upon a successfully grabbing the rtmutex. 1a1fb985f2e2 ("futex: Handle early deadlock
return correctly"), moved the remove_waiter() out of __rt_mutex_start_proxy_lock()
(where 'ret' was only ever 0 or < 0) into the wrapper. Tighten this check to
account for try_to_take_rt_mutex().

Fixes: 3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()")
Change-Id: Ib19a2f223ba67d20496c0ae95096747f5350c520
Reported-by: syzbot+78147abe6c524f183ee9@syzkaller.appspotmail.com
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/69f114ac.050a0220.ac8b.0003.GAE@google.com/
Link: https://patch.msgid.link/20260507112913.1019537-1-dave@stgolabs.net
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>
This commit is contained in:
Davidlohr Bueso
2026-05-07 04:29:13 -07:00
committed by Michael Bestas
parent 46787e4e66
commit 7834037843
1 changed files with 4 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/locking/rtmutex.c
View File

@ -1075,6 +1075,9 @@ static void remove_waiter(struct rt_mutex *lock,
lockdep_assert_held(&lock->wait_lock);
if (!waiter_task) /* never enqueued */
return;
raw_spin_lock(&waiter_task->pi_lock);
rt_mutex_dequeue(lock, waiter);
waiter_task->pi_blocked_on = NULL;
@ -1804,7 +1807,7 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
raw_spin_lock_irq(&lock->wait_lock);
ret = __rt_mutex_start_proxy_lock(lock, waiter, task);
if (unlikely(ret))
if (unlikely(ret < 0))
remove_waiter(lock, waiter);
raw_spin_unlock_irq(&lock->wait_lock);