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). 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.
