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authorDimitris Michailidis <dmichail@google.com>2018-10-19 17:07:13 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-08 11:25:33 +0100
commit0836bdfee568a417ffba238fc180bf5c00c648e3 (patch)
parente92b8475d6d7319bb69c3bdf307f3d9384c3776a (diff)
net: fix pskb_trim_rcsum_slow() with odd trim offset
commit d55bef5059dd057bd077155375c581b49d25be7e upstream. We've been getting checksum errors involving small UDP packets, usually 59B packets with 1 extra non-zero padding byte. netdev_rx_csum_fault() has been complaining that HW is providing bad checksums. Turns out the problem is in pskb_trim_rcsum_slow(), introduced in commit 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"). The source of the problem is that when the bytes we are trimming start at an odd address, as in the case of the 1 padding byte above, skb_checksum() returns a byte-swapped value. We cannot just combine this with skb->csum using csum_sub(). We need to use csum_block_sub() here that takes into account the parity of the start address and handles the swapping. Matches existing code in __skb_postpull_rcsum() and esp_remove_trailer(). Fixes: 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends") Signed-off-by: Dimitris Michailidis <dmichail@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 3 insertions, 2 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3d7c92d38a78..fea7c24e99d0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1509,8 +1509,9 @@ int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
if (skb->ip_summed == CHECKSUM_COMPLETE) {
int delta = skb->len - len;
- skb->csum = csum_sub(skb->csum,
- skb_checksum(skb, len, delta, 0));
+ skb->csum = csum_block_sub(skb->csum,
+ skb_checksum(skb, len, delta, 0),
+ len);
return __pskb_trim(skb, len);