On Wed, 03 Feb 2016 10:35:14 +0100, Takashi Iwai wrote:
On Wed, 03 Feb 2016 09:57:50 +0100, Dmitry Vyukov wrote:
Hello,
The following program triggers an out-of-bounds write in snd_rawmidi_kernel_write1 (run in parallel loop). It seems to try to copy -1 bytes (aka 4GB) from user space into kernel smashing all on its way.
What card is /dev/midi3? Please check /proc/asound/cards. Is it MTPAV?
In anyway the patch below should paper over it. But it's still strange that it gets a negative value there. Could you put
WARN_ON(count1 < 0)
before the newly added check?
I tried it locally with virmidi but it didn't appear, so far. Maybe my setup is too slow and has fewer CPUs than yours.
thanks,
Takashi
--- diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index 26ca02248885..2fef77d9de50 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -1239,6 +1239,8 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, } while (count > 0 && runtime->avail > 0) { count1 = runtime->buffer_size - runtime->appl_ptr; + if (count1 <= 0) + break; if (count1 > count) count1 = count; if (count1 > (long)runtime->avail)