netdev - [PATCH 3.2-3.12] skbuff: skb_segment: orphan frags before copying

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Message-ID: <1397429860.10849.86.camel@deadeye.wl.decadent.org.uk>
Date:	Sun, 13 Apr 2014 23:57:40 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	David Miller <davem@...emloft.net>
Cc:	stable@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev <netdev@...r.kernel.org>
Subject: [PATCH 3.2-3.12] skbuff: skb_segment: orphan frags before copying

From: "Michael S. Tsirkin" <mst@...hat.com>

commit 1fd819ecb90cc9b822cd84d3056ddba315d3340f upstream.

skb_segment copies frags around, so we need
to copy them carefully to avoid accessing
user memory after reporting completion to userspace
through a callback.

skb_segment doesn't normally happen on datapath:
TSO needs to be disabled - so disabling zero copy
in this case does not look like a big deal.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2.  As skb_segment() only supports page-frags *or* a
 frag list, there is no need for the additional frag_skb pointer or the
 preparatory renaming.]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
For branches older than 3.6, commit a353e0ce0fd4 ('skbuff: add an api to
orphan frags') is needed before this.  This is untested and I would
appreciate a review.

Ben.
---
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2699,6 +2699,9 @@ struct sk_buff *skb_segment(struct sk_bu
 						 skb_put(nskb, hsize), hsize);
 
 		while (pos < offset + len && i < nfrags) {
+			if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
+				goto err;
+
 			*frag = skb_shinfo(skb)->frags[i];
 			__skb_frag_ref(frag);
 			size = skb_frag_size(frag);


-- 
Ben Hutchings
I haven't lost my mind; it's backed up on tape somewhere.

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