Subject: [PATCH 28/55] sctp: remove sctp_chunk_put from fail_mark err path in sctp_ulpevent_make_rcvmsg

From: Xin Long <[email-masked]>
Date: Thu, 10 May 2018 17:34:13 +0800

[ Upstream commit 6910e25de2257e2c82c7a2d126e3463cd8e50810 ]

In Commit 1f45f78f8e51 ("sctp: allow GSO frags to access the chunk too"),
it held the chunk in sctp_ulpevent_make_rcvmsg to access it safely later
in recvmsg. However, it also added sctp_chunk_put in fail_mark err path,
which is only triggered before holding the chunk.

syzbot reported a use-after-free crash happened on this err path, where
it shouldn't call sctp_chunk_put.

This patch simply removes this call.

Fixes: 1f45f78f8e51 ("sctp: allow GSO frags to access the chunk too")
Reported-by: [email-masked]
Signed-off-by: Xin Long <[email-masked]>
Acked-by: Neil Horman <[email-masked]>
Acked-by: Marcelo Ricardo Leitner <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/sctp/ulpevent.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
index 84207ad33e8e..8cb7d9858270 100644
--- a/net/sctp/ulpevent.c
+++ b/net/sctp/ulpevent.c
@@ -715,7 +715,6 @@ struct sctp_ulpevent *sctp_ulpevent_make_rcvmsg(struct sctp_association *asoc,
 	return event;
 
 fail_mark:
-	sctp_chunk_put(chunk);
 	kfree_skb(skb);
 fail:
 	return NULL;
-- 
2.14.3