3.16.61-rc1 review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
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 Signed-off-by: Takashi Iwai tiwai@suse.de [bwh: Backported to 3.16: adjust context, indentation] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/core/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1476,7 +1476,7 @@ static int snd_timer_user_next_device(st } else { if (id.subdevice < 0) { id.subdevice = 0; - } else { + } else if (id.subdevice < INT_MAX) { id.subdevice++; } }