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@suse.de>

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index ea2d0ae85bd367d5ea70068ee74d925a349789c3..f2343f63ba26b149455cd29ae77f85c8a67e6579 100644 (file)
--- 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);