Patch "sctp: sctp should release assoc when sctp_make_abort_user return NULL in sctp_close" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

sctp: sctp should release assoc when sctp_make_abort_user return NULL in sctp_close

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sctp-sctp-should-release-assoc-when-sctp_make_abort_user-return-null-in-sctp_close.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Tue, 29 Dec 2015 17:49:25 +0800
Subject: sctp: sctp should release assoc when sctp_make_abort_user return NULL in sctp_close

From: Xin Long <[email protected]>

[ Upstream commit 068d8bd338e855286aea54e70d1c101569284b21 ]

In sctp_close, sctp_make_abort_user may return NULL because of memory allocation failure. If this happens, it will bypass any state change and never free the assoc. The assoc has no chance to be freed and it will be kept in memory with the state it had even after the socket is closed by sctp_close().

So if sctp_make_abort_user fails to allocate memory, we should abort the asoc via sctp_primitive_ABORT as well. Just like the annotation in sctp_sf_cookie_wait_prm_abort and sctp_sf_do_9_1_prm_abort said, "Even if we can't send the ABORT due to low memory delete the TCB. This is a departure from our typical NOMEM handling".

But then the chunk is NULL (low memory) and the SCTP_CMD_REPLY cmd would dereference the chunk pointer, and system crash. So we should add SCTP_CMD_REPLY cmd only when the chunk is not NULL, just like other places where it adds SCTP_CMD_REPLY cmd.

---
 net/sctp/sm_statefuns.c |    6 ++++--
 net/sctp/socket.c       |    3 +--
 2 files changed, 5 insertions(+), 4 deletions(-)

@@ -4829,7 +4829,8 @@ sctp_disposition_t sctp_sf_do_9_1_prm_ab
 
 	retval = SCTP_DISPOSITION_CONSUME;
 
-	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
+	if (abort)
+		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
 
 	/* Even if we can't send the ABORT due to low memory delete the
 	 * TCB.  This is a departure from our typical NOMEM handling.

@@ -4966,7 +4967,8 @@ sctp_disposition_t sctp_sf_cookie_wait_p
 			SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
 	retval = SCTP_DISPOSITION_CONSUME;
 
-	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
+	if (abort)
+		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
 
 	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
 			SCTP_STATE(SCTP_STATE_CLOSED));

@@ -1513,8 +1513,7 @@ static void sctp_close(struct sock *sk,
 			struct sctp_chunk *chunk;
 
 			chunk = sctp_make_abort_user(asoc, NULL, 0);
-			if (chunk)
-				sctp_primitive_ABORT(net, asoc, chunk);
+			sctp_primitive_ABORT(net, asoc, chunk);
 		} else
 			sctp_primitive_SHUTDOWN(net, asoc, NULL);
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/sctp-sctp-should-release-assoc-when-sctp_make_abort_user-return-null-in-sctp_close.patch