4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/core/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1517,7 +1517,7 @@ 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++; } }
