linux-kernel - [PATCH 4.19 37/42] sctp: not increase streams incnt before sending addstrm

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Date:   Wed, 21 Nov 2018 20:06:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jianwen Ji <jiji@...hat.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 37/42] sctp: not increase streams incnt before sending addstrm_in request

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

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

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

[ Upstream commit e1e46479847e66f78f79d8c24d5169a5954b3fc2 ]

Different from processing the addstrm_out request, The receiver handles
an addstrm_in request by sending back an addstrm_out request to the
sender who will increase its stream's in and incnt later.

Now stream->incnt has been increased since it sent out the addstrm_in
request in sctp_send_add_streams(), with the wrong stream->incnt will
even cause crash when copying stream info from the old stream's in to
the new one's in sctp_process_strreset_addstrm_out().

This patch is to fix it by simply removing the stream->incnt change
from sctp_send_add_streams().

Fixes: 242bd2d519d7 ("sctp: implement sender-side procedures for Add Incoming/Outgoing Streams Request Parameter")
Reported-by: Jianwen Ji <jiji@...hat.com>
Signed-off-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sctp/stream.c |    1 -
 1 file changed, 1 deletion(-)

--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -535,7 +535,6 @@ int sctp_send_add_streams(struct sctp_as
 		goto out;
 	}

-	stream->incnt = incnt;
 	stream->outcnt = outcnt;

 	asoc->strreset_outstanding = !!out + !!in;