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tcp: skb_shift cannot cache frag ptrs past pskb_expand_head

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Since pskb_expand_head creates copy of the shared area we
cannot keep any frag ptr past de-cloning. This fixes the
tcpdump recvfrom -EFAULT problem.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2008-11-25 13:57:01 -08:00 committed by David S. Miller
parent f6486d40b3
commit 9f782db3f5
1 changed files with 6 additions and 1 deletions
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7
net/core/skbuff.c
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@ -2018,7 +2018,10 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
skb_split_no_header(skb, skb1, len, pos); skb_split_no_header(skb, skb1, len, pos);
} }
/* Shifting from/to a cloned skb is a no-go. */ /* Shifting from/to a cloned skb is a no-go.
*
* Caller cannot keep skb_shinfo related pointers past calling here!
*/
static int skb_prepare_for_shift(struct sk_buff *skb) static int skb_prepare_for_shift(struct sk_buff *skb)
{ {
return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC); return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
@ -2070,6 +2073,8 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen)
skb_prepare_for_shift(tgt)) skb_prepare_for_shift(tgt))
return 0; return 0;
/* All previous frag pointers might be stale! */
fragfrom = &skb_shinfo(skb)->frags[from];
fragto = &skb_shinfo(tgt)->frags[merge]; fragto = &skb_shinfo(tgt)->frags[merge];
fragto->size += shiftlen; fragto->size += shiftlen;