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skbuff: skb_segment: orphan frags before copying

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>
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1 parent 1a4ceda commit 1fd819ecb90cc9b822cd84d3056ddba315d3340f @mstsirkin mstsirkin committed with davem330 Mar 10, 2014
Showing with 6 additions and 0 deletions.
  1. +6 −0 net/core/skbuff.c
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@@ -2854,6 +2854,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
skb_frag_t *frag = skb_shinfo(head_skb)->frags;
unsigned int mss = skb_shinfo(head_skb)->gso_size;
unsigned int doffset = head_skb->data - skb_mac_header(head_skb);
+ struct sk_buff *frag_skb = head_skb;
unsigned int offset = doffset;
unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
unsigned int headroom;
@@ -2898,6 +2899,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
i = 0;
nfrags = skb_shinfo(list_skb)->nr_frags;
frag = skb_shinfo(list_skb)->frags;
+ frag_skb = list_skb;
pos += skb_headlen(list_skb);
while (pos < offset + len) {
@@ -2985,6 +2987,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
i = 0;
nfrags = skb_shinfo(list_skb)->nr_frags;
frag = skb_shinfo(list_skb)->frags;
+ frag_skb = list_skb;
BUG_ON(!nfrags);
@@ -2999,6 +3002,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
goto err;
}
+ if (unlikely(skb_orphan_frags(frag_skb, GFP_ATOMIC)))
+ goto err;
+
*nskb_frag = *frag;
__skb_frag_ref(nskb_frag);
size = skb_frag_size(nskb_frag);

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