linux-kernel - [PATCH 3.2 198/199] sctp: avoid BUG_ON on sctp_wait_for

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Date:   Fri, 10 Mar 2017 11:46:10 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Alexander Popov" <alex.popov@...ux.com>,
        "Marcelo Ricardo Leitner" <marcelo.leitner@...il.com>,
        "Xin Long" <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 198/199] sctp: avoid BUG_ON on sctp_wait_for_sndbuf

3.2.87-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

commit 2dcab598484185dea7ec22219c76dcdd59e3cb90 upstream.

Alexander Popov reported that an application may trigger a BUG_ON in
sctp_wait_for_sndbuf if the socket tx buffer is full, a thread is
waiting on it to queue more data and meanwhile another thread peels off
the association being used by the first thread.

This patch replaces the BUG_ON call with a proper error handling. It
will return -EPIPE to the original sendmsg call, similarly to what would
have been done if the association wasn't found in the first place.

Acked-by: Alexander Popov <alex.popov@...ux.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Reviewed-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/sctp/socket.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6492,7 +6492,8 @@ static int sctp_wait_for_sndbuf(struct s
 		 */
 		sctp_release_sock(sk);
 		current_timeo = schedule_timeout(current_timeo);
-		BUG_ON(sk != asoc->base.sk);
+		if (sk != asoc->base.sk)
+			goto do_error;
 		sctp_lock_sock(sk);
 
 		*timeo_p = current_timeo;