From 00d9e47f8ec2a293db9ebed86aab0583d9a49533 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 5 Sep 2019 14:03:40 +0200 Subject: [PATCH] posix-cpu-timers: Always clear head pointer on dequeue The head pointer in struct cpu_timer is checked to be NULL in posix_cpu_timer_del() when the delete raced with the exit cleanup. The works correctly as long as the timer is actually dequeued via posix_cpu_timers_exit*(). But if the timer was dequeued due to expiry the head pointer is still set and triggers the warning. In fact keeping the head pointer around after any dequeue is pointless as is has no meaning at all after that. Clear the head pointer always on dequeue and remove the unused requeue function while at it. Fixes: 60bda037f1dd ("posix-cpu-timers: Utilize timerqueue for storage") Reported-by: syzbot+55acd54b57bb4b3840a4@syzkaller.appspotmail.com Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/20190905120539.707986830@linutronix.de --- include/linux/posix-timers.h | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index e685916551bf..3d10c84a97a9 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -74,11 +74,6 @@ struct cpu_timer { int firing; }; -static inline bool cpu_timer_requeue(struct cpu_timer *ctmr) -{ - return timerqueue_add(ctmr->head, &ctmr->node); -} - static inline bool cpu_timer_enqueue(struct timerqueue_head *head, struct cpu_timer *ctmr) { @@ -88,8 +83,10 @@ static inline bool cpu_timer_enqueue(struct timerqueue_head *head, static inline void cpu_timer_dequeue(struct cpu_timer *ctmr) { - if (!RB_EMPTY_NODE(&ctmr->node.node)) + if (ctmr->head) { timerqueue_del(ctmr->head, &ctmr->node); + ctmr->head = NULL; + } } static inline u64 cpu_timer_getexpires(struct cpu_timer *ctmr)