Re: [syzbot] [kernel?] general protection fault in remove_waiter

[Hillf Danton]

> Date: Tue, 28 Apr 2026 13:12:28 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    897d54018cc9 Merge tag 'fbdev-for-7.1-rc1-2' of git://git...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=172c32ce580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=59da38148f3a3d24
> dashboard link: https://syzkaller.appspot.com/bug?extid=78147abe6c524f183ee9
> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10c7f273980000

#syz test

--- x/kernel/locking/rtmutex.c
+++ y/kernel/locking/rtmutex.c
@@ -1558,6 +1558,8 @@ static void __sched remove_waiter(struct
 
 	lockdep_assert_held(&lock->wait_lock);
 
+	if (!waiter_task)
+		return;
 	scoped_guard(raw_spinlock, &waiter_task->pi_lock) {
 		rt_mutex_dequeue(lock, waiter);
 		waiter_task->pi_blocked_on = NULL;
--