From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 10 May 2018 17:34:13 +0800
Subject: sctp: remove sctp_chunk_put from fail_mark err path in
 sctp_ulpevent_make_rcvmsg
Git-commit: 6910e25de2257e2c82c7a2d126e3463cd8e50810
Patch-mainline: v4.17-rc5
References: networking-stable-18_05_15

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: syzbot+141d898c5f24489db4aa@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 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;
-- 
2.18.0