skbuff: skb_segment: orphan frags before copying

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@redhat.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.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@decadent.org.uk>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index e6289b474fe2d923412e8a18c040c8f461f335d9..7121d9b59bbddf58d63b07dbf18751d307f681bb 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2698,6 +2698,9 @@ struct sk_buff *skb_segment(struct sk_buff *skb, u32 features)
                                                 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);