On Wed, Jun 2, 2021 at 10:19 PM Jaroslav Kysela perex@perex.cz 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...@syzkaller.appspotmail.com
================================================================================ 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/soun...
-- My best regards to you.
No System Is Safe! Dongliang Mu-- Jaroslav Kysela perex@perex.cz Linux Sound Maintainer; ALSA Project; Red Hat, Inc.