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authorEric Dumazet <edumazet@google.com>2021-12-04 07:53:56 +0300
committerJakub Kicinski <kuba@kernel.org>2021-12-07 03:26:46 +0300
commit45cac6754529ae17345d8f5b632d9e602a091a20 (patch)
tree711a5790a06b73816234f0c860caae947edc5cbe /include/linux/skbuff.h
parent4c375272fb0ba19288e323928d1f6937e368851f (diff)
downloadlinux-45cac6754529ae17345d8f5b632d9e602a091a20.tar.xz
net: fix recent csum changes
Vladimir reported csum issues after my recent change in skb_postpull_rcsum() Issue here is the following: initial skb->csum is the csum of [part to be pulled][rest of packet] Old code: skb->csum = csum_sub(skb->csum, csum_partial(pull, pull_length, 0)); New code: skb->csum = ~csum_partial(pull, pull_length, ~skb->csum); This is broken if the csum of [pulled part] happens to be equal to skb->csum, because end result of skb->csum is 0 in new code, instead of being 0xffffffff David Laight suggested to use skb->csum = -csum_partial(pull, pull_length, -skb->csum); I based my patches on existing code present in include/net/seg6.h, update_csum_diff4() and update_csum_diff16() which might need a similar fix. I guess that my tests, mostly pulling 40 bytes of IPv6 header were not providing enough entropy to hit this bug. v2: added wsum_negate() to make sparse happy. Fixes: 29c3002644bd ("net: optimize skb_postpull_rcsum()") Fixes: 0bd28476f636 ("gro: optimize skb_gro_postpull_rcsum()") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Vladimir Oltean <vladimir.oltean@nxp.com> Suggested-by: David Laight <David.Laight@ACULAB.COM> Cc: David Lebrun <dlebrun@google.com> Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20211204045356.3659278-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/linux/skbuff.h')
-rw-r--r--include/linux/skbuff.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index eae4bd3237a4..dd262bd8ddbe 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3486,7 +3486,8 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
const void *start, unsigned int len)
{
if (skb->ip_summed == CHECKSUM_COMPLETE)
- skb->csum = ~csum_partial(start, len, ~skb->csum);
+ skb->csum = wsum_negate(csum_partial(start, len,
+ wsum_negate(skb->csum)));
else if (skb->ip_summed == CHECKSUM_PARTIAL &&
skb_checksum_start_offset(skb) < 0)
skb->ip_summed = CHECKSUM_NONE;