On Wed, 01 Nov 2017 19:39:46 +0100, Dmitry Vyukov wrote: > > On Wed, Nov 1, 2017 at 9:38 PM, syzbot > <bot+31681772ec7a18dde8d3f8caf475f361a89b9514@xxxxxxxxxxxxxxxxxxxxxxxxx> > wrote: > > Hello, > > > > syzkaller hit the following crash on > > fc2e8b1a47c14b22c33eb087fca0db58e1f4ed0e > > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > > compiler: gcc (GCC) 7.1.1 20170620 > > .config is attached > > Raw console output is attached. > > C reproducer is attached > > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > > for information about syzkaller reproducers > > This also happened on more recent commits, including upstream > 9c323bff13f92832e03657cabdd70d731408d621 (Oct 20): Could you try the patch below with CONFIG_SND_DEBUG=y and see whether it catches any bad calls? It's already in for-next branch for 4.15. thanks, Takashi -- 8< -- From: Takashi Iwai <tiwai@xxxxxxx> Subject: [PATCH] ALSA: seq: Add sanity check for user-space pointer delivery The sequencer event may contain a user-space pointer with its SNDRV_SEQ_EXT_USRPTR bit, and we assure that its delivery is limited with non-atomic mode. Otherwise the copy_from_user() may hit the fault and cause a problem. Although the core code doesn't set such a flag (only set at snd_seq_write()), any wild driver may set it mistakenly and lead to an unexpected crash. This patch adds a sanity check of such events at the delivery core code to filter out the invalid invocation in the atomic mode. Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> --- sound/core/seq/seq_clientmgr.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index ea2d0ae85bd3..f2343f63ba26 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -802,6 +802,10 @@ static int snd_seq_deliver_event(struct snd_seq_client *client, struct snd_seq_e return -EMLINK; } + if (snd_seq_ev_is_variable(event) && + snd_BUG_ON(atomic && (event->data.ext.len & SNDRV_SEQ_EXT_USRPTR))) + return -EINVAL; + if (event->queue == SNDRV_SEQ_ADDRESS_SUBSCRIBERS || event->dest.client == SNDRV_SEQ_ADDRESS_SUBSCRIBERS) result = deliver_to_subscribers(client, event, atomic, hop); -- 2.14.2 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
