[PATCH 40/61] SCTP: Always linearise packet on input

[Chris Wright <chrisw@sous-sol.org>]

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

From: Herbert Xu <herbert@gondor.apana.org.au>

I was looking at a RHEL5 bug report involving Xen and SCTP
(https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=212550).
It turns out that SCTP wasn't written to handle skb fragments at
all.  The absence of any calls to skb_may_pull is testament to
that.

It just so happens that Xen creates fragmented packets more often
than other scenarios (header & data split when going from domU to
dom0).  That's what caused this bug to show up.

Until someone has the time sits down and audits the entire net/sctp
directory, here is a conservative and safe solution that simply
linearises all packets on input.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

---
 net/sctp/input.c |    3 +++
 1 file changed, 3 insertions(+)

--- linux-2.6.18.1.orig/net/sctp/input.c
+++ linux-2.6.18.1/net/sctp/input.c
@@ -135,6 +135,9 @@ int sctp_rcv(struct sk_buff *skb)
 
 	SCTP_INC_STATS_BH(SCTP_MIB_INSCTPPACKS);
 
+	if (skb_linearize(skb))
+		goto discard_it;
+
 	sh = (struct sctphdr *) skb->h.raw;
 
 	/* Pull up the IP and SCTP headers. */

--
-
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