ALSA: timer: Fix UBSAN warning at SNDRV_TIMER_IOCTL_NEXT_DEVICE ioctl
authorTakashi Iwai <tiwai@suse.de>
Mon, 25 Jun 2018 09:09:11 +0000 (11:09 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 3 Jul 2018 09:25:04 +0000 (11:25 +0200)
commit69f96e9b570a7e09e8493a50068d08174ce3a3a2
treee019df3becba6bf45d28590d80f14819ab943ee3
parent3d1de95138fbf54bab0049ae669299e3f1a4c4fe
ALSA: timer: Fix UBSAN warning at SNDRV_TIMER_IOCTL_NEXT_DEVICE ioctl

commit b41f794f284966fd6ec634111e3b40d241389f96 upstream.

The kernel may spew a WARNING about UBSAN undefined behavior at
handling ALSA timer ioctl SNDRV_TIMER_IOCTL_NEXT_DEVICE:

UBSAN: Undefined behaviour in sound/core/timer.c:1524:19
signed integer overflow:
2147483647 + 1 cannot be represented in type 'int'
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x122/0x1c8 lib/dump_stack.c:113
 ubsan_epilogue+0x12/0x86 lib/ubsan.c:159
 handle_overflow+0x1c2/0x21f lib/ubsan.c:190
 __ubsan_handle_add_overflow+0x2a/0x31 lib/ubsan.c:198
 snd_timer_user_next_device sound/core/timer.c:1524 [inline]
 __snd_timer_user_ioctl+0x204d/0x2520 sound/core/timer.c:1939
 snd_timer_user_ioctl+0x67/0x95 sound/core/timer.c:1994
 ....

It happens only when a value with INT_MAX is passed, as we're
incrementing it unconditionally.  So the fix is trivial, check the
value with INT_MAX.  Although the bug itself is fairly harmless, it's
better to fix it so that fuzzers won't hit this again later.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200213
Reported-and-tested-by: Team OWL337 <icytxw@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sound/core/timer.c