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Commit 31b33dfb authored by Pravin B Shelar's avatar Pravin B Shelar Committed by David S. Miller
Browse files

skbuff: Fix skb checksum partial check. 



Earlier patch 6ae459bd 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: 6ae459bd ("skbuff: Fix skb checksum flag on skb pull")
Reported-by: default avatarAndrew Vagin <avagin@odin.com>
Signed-off-by: default avatarPravin B Shelar <pshelar@nicira.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 741a11d9

include/linux/skbuff.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -2708,7 +2708,7 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb, 
	if (skb->ip_summed == CHECKSUM_COMPLETE)

	if (skb->ip_summed == CHECKSUM_COMPLETE)

		skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));

		skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));

	else if (skb->ip_summed == CHECKSUM_PARTIAL &&

	else if (skb->ip_summed == CHECKSUM_PARTIAL &&

		 skb_checksum_start_offset(skb) <= len)

		 skb_checksum_start_offset(skb) < 0)

		skb->ip_summed = CHECKSUM_NONE;

		skb->ip_summed = CHECKSUM_NONE;

}

}

net/core/skbuff.c

+5 −4
Original line number Original line Diff line number Diff line
@@ -2958,11 +2958,12 @@ EXPORT_SYMBOL_GPL(skb_append_pagefrags); 
 */

 */

unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)

unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)

{

{

	unsigned char *data = skb->data;



	BUG_ON(len > skb->len);

	BUG_ON(len > skb->len);

	skb->len -= len;

	__skb_pull(skb, len);

	BUG_ON(skb->len < skb->data_len);

	skb_postpull_rcsum(skb, data, len);

	skb_postpull_rcsum(skb, skb->data, len);

	return skb->data;

	return skb->data += len;

}

}

EXPORT_SYMBOL_GPL(skb_pull_rcsum);

EXPORT_SYMBOL_GPL(skb_pull_rcsum);