Commit f03a8061 authored by Pravin B Shelar's avatar Pravin B Shelar Committed by Greg Kroah-Hartman

skbuff: Fix skb checksum partial check.

[ Upstream commit 31b33dfb0a144469dd805514c9e63f4993729a48 ]

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: default avatarAndrew Vagin <>
Signed-off-by: default avatarPravin B Shelar <>
Signed-off-by: default avatarDavid S. Miller <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 275ceb01
......@@ -2364,7 +2364,7 @@ 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;
......@@ -2711,11 +2711,12 @@ EXPORT_SYMBOL(skb_append_datato_frags);
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;
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