On Wed, 20 Apr 2016 10:08:55 +0200, Takashi Iwai wrote: > > On Wed, 20 Apr 2016 09:56:04 +0200, > Dmitry Vyukov wrote: > > > > On Sun, Apr 3, 2016 at 8:33 AM, Takashi Iwai <tiwai@xxxxxxx> wrote: > > >> >> It is not easily reproducible. I've hit several times while running > > >> >> fuzzer for a week. Here is one of the logs for the record: > > >> >> https://gist.githubusercontent.com/dvyukov/c84798ee55721563ecb537c4d51dc9f5/raw/f00b865a85877656f13b41917f7321730f140d35/gistfile1.txt > > >> > > > >> > There are a few more fixes in sound/core/timer.c since 4.5, and they > > >> > possibly already cover this. > > >> > > > >> > Please let me know if this is still seen on the upcoming 4.6-rc2. > > >> > > >> Hi Takashi, > > >> > > >> I've updated fuzzer to 05cf8077e54b20dddb756eaa26f3aeb5c38dd3cf (Apr > > >> 1) yesterday. Let's see if it still happens. > > >> > > >> Out of curiosity, how was the bug found? > > > > > > Well, I'm not entirely sure whether they really cover. It's just a > > > hope, as these are patches to close some possible races :) > > > > > > 9984d1b5835ca29fc7025186a891ee7398d21cc7 > > > ALSA: timer: Protect the whole snd_timer_close() with open race > > > f65e0d299807d8a11812845c972493c3f9a18e10 > > > ALSA: timer: Call notifier in the same spinlock > > > 4a07083ed613644c96c34a7dd2853dc5d7c70902 > > > ALSA: timer: Use mod_timer() for rearming the system timer > > > > > > Hi Takashi, > > > > I've hit it again on 806fdcce017dc98c4dbf8ed001750a0d7d2bb0af (Apr > > 14), all 3 commits are already in my tree. > > > > [ 343.222218] ------------[ cut here ]------------ > > [ 343.222218] WARNING: CPU: 3 PID: 7040 at kernel/time/hrtimer.c:837 > > hrtimer_forward+0x26a/0x3e0 > > This is a different warning. The previous was use-after-free, and > this is a warning about re-arming the queued hrtimer. > Maybe there is a slightly remaining race about hrtimer_start() and the > interrupt handler in snd-hrtimer. Could you check whether two patches below help anything? This should harden against the race between hrtimer callback and another start/stop calls. Takashi
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0001-ALSA-timer-Allow-backend-disabling-start-stop-from-h.patch
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0002-ALSA-hrtimer-Use-manual-start-stop-in-callback.patch
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