From 19b592dae895aad10b84246b0e12caad04e9eb0d Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 9 Oct 2017 17:05:35 +0200
Subject: [PATCH] ALSA: seq: Add sanity check for user-space pointer delivery
Git-commit: 19b592dae895aad10b84246b0e12caad04e9eb0d
Patch-mainline: v4.15-rc1
References: bsc#1121278
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>
---
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);
--
2.20.1