On Wed, 02 Jun 2021 16:19:13 +0200, Jaroslav Kysela 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). I've already submitted the fix patch, but it doesn't seem reaching properly to ML. Hmm. Will resend. Takashi
