[3.13.y-ckt stable] Patch "net: sctp: use MAX_HEADER for headroom reserve in output path" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    net: sctp: use MAX_HEADER for headroom reserve in output path

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 1d998004296a804e6dc83c331f5acc3baa4093d0 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman at redhat.com>
Date: Wed, 3 Dec 2014 12:13:58 +0100
Subject: net: sctp: use MAX_HEADER for headroom reserve in output path
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[ Upstream commit 9772b54c55266ce80c639a80aa68eeb908f8ecf5 ]

To accomodate for enough headroom for tunnels, use MAX_HEADER instead
of LL_MAX_HEADER. Robert reported that he has hit after roughly 40hrs
of trinity an skb_under_panic() via SCTP output path (see reference).
I couldn't reproduce it from here, but not using MAX_HEADER as elsewhere
in other protocols might be one possible cause for this.

In any case, it looks like accounting on chunks themself seems to look
good as the skb already passed the SCTP output path and did not hit
any skb_over_panic(). Given tunneling was enabled in his .config, the
headroom would have been expanded by MAX_HEADER in this case.

Reported-by: Robert Święcki <robert at swiecki.net>
Reference: https://lkml.org/lkml/2014/12/1/507
Fixes: 594ccc14dfe4d ("[SCTP] Replace incorrect use of dev_alloc_skb with alloc_skb in sctp_packet_transmit().")
Signed-off-by: Daniel Borkmann <dborkman at redhat.com>
Acked-by: Vlad Yasevich <vyasevich at gmail.com>
Acked-by: Neil Horman <nhorman at tuxdriver.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sctp/output.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/output.c b/net/sctp/output.c
index e867326..777dba7 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -402,12 +402,12 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	sk = chunk->skb->sk;

 	/* Allocate the new skb.  */
-	nskb = alloc_skb(packet->size + LL_MAX_HEADER, GFP_ATOMIC);
+	nskb = alloc_skb(packet->size + MAX_HEADER, GFP_ATOMIC);
 	if (!nskb)
 		goto nomem;

 	/* Make sure the outbound skb has enough header room reserved. */
-	skb_reserve(nskb, packet->overhead + LL_MAX_HEADER);
+	skb_reserve(nskb, packet->overhead + MAX_HEADER);

 	/* Set the owning socket so that we know where to get the
 	 * destination IP address.
--
1.9.1