sctp: remove sctp_chunk_put from fail_mark err path in sctp_ulpevent_make_rcvmsg

[ Upstream commit 6910e25 ]

In Commit 1f45f78 ("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: 1f45f78 ("sctp: allow GSO frags to access the chunk too")
Reported-by: [email protected]
Signed-off-by: Xin Long <[email protected]>
Acked-by: Neil Horman <[email protected]>
Acked-by: Marcelo Ricardo Leitner <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: lxin

net/sctp/ulpevent.c

@@ -717,7 +717,6 @@ 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;