3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> commit 4b0c0f294f60abcdd20994a8341a95c8ac5eeb96 upstream. Prarit reported a crash on CPU offline/online. The reason is that on CPU down the NOHZ related per cpu data of the dead cpu is not cleaned up. If at cpu online an interrupt happens before the per cpu tick device is registered the irq_enter() check potentially sees stale data and dereferences a NULL pointer. Cleanup the data after the cpu is dead. Reported-by: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Mike Galbraith <bitbucket@xxxxxxxxx> Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305031451561.2886@ionos Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -866,7 +866,7 @@ void tick_cancel_sched_timer(int cpu) hrtimer_cancel(&ts->sched_timer); # endif - ts->nohz_mode = NOHZ_MODE_INACTIVE; + memset(ts, 0, sizeof(*ts)); } #endif -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html