On Wed, Jun 2, 2021 at 10:19 PM Jaroslav Kysela <perex@xxxxxxxx> wrote: > > On 02. 06. 21 15:18, Dongliang Mu wrote: > >> Hello, > >> > >> syzbot found the following issue on: > >> > >> HEAD commit: 5ff2756a Merge tag 'nfs-for-5.13-2' of git://git.linux-nfs.. > >> git tree: upstream > >> console output: https://syzkaller.appspot.com/x/log.txt?x=17872d5bd00000 > >> kernel config: https://syzkaller.appspot.com/x/.config?x=770708ea7cfd4916 > >> dashboard link: https://syzkaller.appspot.com/bug?extid=d102fa5b35335a7e544e > >> > >> Unfortunately, I don't have any reproducer for this issue yet. > >> > >> IMPORTANT: if you fix the issue, please add the following tag to the commit: > >> Reported-by: syzbot+d102fa...@xxxxxxxxxxxxxxxxxxxxxxxxx > >> > >> ================================================================================ > >> UBSAN: shift-out-of-bounds in sound/core/timer.c:1376:23 > >> shift exponent 105 is too large for 32-bit type 'int' > >> CPU: 1 PID: 10368 Comm: syz-executor.1 Not tainted 5.13.0-rc3-syzkaller #0 > >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > >> Call Trace: > >> __dump_stack lib/dump_stack.c:79 [inline] > >> dump_stack+0x141/0x1d7 lib/dump_stack.c:120 > >> ubsan_epilogue+0xb/0x5a lib/ubsan.c:148 > >> __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:327 > >> snd_timer_user_ccallback.cold+0x19/0x1e sound/core/timer.c:1376 > >> > >> snd_timer_notify1+0x243/0x3b0 sound/core/timer.c:525 > > > > The root cause of this bug is in the snd_timer_notify1 [1]. At the end > > of this function, it calls "ts->ccallback(ts, event + 100, &tstamp, > > resolution)". > > > > Here the variable event is 5. It adds 100 and is passed as 2nd > > argument of snd_timer_user_ccallback. > > > >>From the variable naming, the 2nd argument should an event, and in the > > range of event enumeration. In fact, 105 (event + 100) is out of this > > range. I don't quite understand the meaning of adding 100. Any thought > > here? > > It seems that the original intent was to move the event to the M... events: > > SNDRV_TIMER_EVENT_MSTART = SNDRV_TIMER_EVENT_START + 10, > > So the added value should be 10 which should not break the shift range (8 > /resume/ + 10 = 18). It seems you are right. Then event should be between SNDRV_TIMER_EVENT_MSTART and SNDRV_TIMER_EVENT_MPAUSE. I double check all the ccallback site, only snd_timer_notify1 invokes ccallback with event + 100, others seem ok. 1 timer.c snd_timer_notify1 515 if (ti->ccallback) 2 timer.c snd_timer_notify1 516 ti->ccallback(ti, event, &tstamp, resolution); 3 timer.c snd_timer_notify1 524 if (ts->ccallback) 4 timer.c snd_timer_notify1 525 ts->ccallback(ts, event + 100, &tstamp, resolution); 5 timer.c snd_timer_notify 1092 if (ti->ccallback) 6 timer.c snd_timer_notify 1093 ti->ccallback(ti, event, tstamp, resolution); 7 timer.c snd_timer_notify 1095 if (ts->ccallback) 8 timer.c snd_timer_notify 1096 ts->ccallback(ts, event, tstamp, resolution); 9 timer.c snd_timer_user_tselect 1782 tu->timeri->ccallback = snd_timer_user_ccallback; a aloop.c loopback_snd_timer_open 1137 timeri->ccallback = loopback_snd_timer_event; > > Jaroslav > > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/core/timer.c?id=5ff2756afde08b266fbb673849899fec694f39f1#n497 > > > > -- > > My best regards to you. > > > > No System Is Safe! > > Dongliang Mu > > > > > -- > Jaroslav Kysela <perex@xxxxxxxx> > Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
