linux-kernel - [PATCH 4.16 26/55] sctp: remove sctp_chunk_put from fail_mark err path in sctp_ulpevent_make

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Date:   Fri, 18 May 2018 10:15:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+141d898c5f24489db4aa@...kaller.appspotmail.com,
        Xin Long <lucien.xin@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.16 26/55] sctp: remove sctp_chunk_put from fail_mark err path in sctp_ulpevent_make_rcvmsg

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@...il.com>

[ 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: syzbot+141d898c5f24489db4aa@...kaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@...il.com>
Acked-by: Neil Horman <nhorman@...driver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sctp/ulpevent.c |    1 -
 1 file changed, 1 deletion(-)

--- a/net/sctp/ulpevent.c
+++ b/net/sctp/ulpevent.c
@@ -715,7 +715,6 @@ struct sctp_ulpevent *sctp_ulpevent_make
 	return event;
 
 fail_mark:
-	sctp_chunk_put(chunk);
 	kfree_skb(skb);
 fail:
 	return NULL;