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skbuff: Fix skb checksum partial check.

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Earlier patch 6ae459bda tried to detect void ckecksum partial
skb by comparing pull length to checksum offset. But it does
not work for all cases since checksum-offset depends on
updates to skb->data.

Following patch fixes it by validating checksum start offset
after skb-data pointer is updated. Negative value of checksum
offset start means there is no need to checksum.

Fixes: 6ae459bda ("skbuff: Fix skb checksum flag on skb pull")
Reported-by: Andrew Vagin <avagin@odin.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pravin B Shelar 2015-09-28 17:24:25 -07:00 committed by David S. Miller
parent 741a11d9e4
commit 31b33dfb0a
2 changed files with 6 additions and 5 deletions
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2
include/linux/skbuff.h
View File

@ -2708,7 +2708,7 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
else if (skb->ip_summed == CHECKSUM_PARTIAL &&
skb_checksum_start_offset(skb) <= len)
skb_checksum_start_offset(skb) < 0)
skb->ip_summed = CHECKSUM_NONE;
}

9
net/core/skbuff.c
View File

@ -2958,11 +2958,12 @@ EXPORT_SYMBOL_GPL(skb_append_pagefrags);
*/
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
{
unsigned char *data = skb->data;
BUG_ON(len > skb->len);
skb->len -= len;
BUG_ON(skb->len < skb->data_len);
skb_postpull_rcsum(skb, skb->data, len);
return skb->data += len;
__skb_pull(skb, len);
skb_postpull_rcsum(skb, data, len);
return skb->data;
}
EXPORT_SYMBOL_GPL(skb_pull_rcsum);