diff options
authorDimitris Michailidis <dmichail@google.com>2018-10-19 17:07:13 -0700
committerDavid S. Miller <davem@davemloft.net>2018-10-20 01:13:42 -0700
commitd55bef5059dd057bd077155375c581b49d25be7e (patch)
parent48995423143a097527802e28d7add20e5a27677a (diff)
net: fix pskb_trim_rcsum_slow() with odd trim offset
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>
1 files changed, 3 insertions, 2 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 428094b577fc..f817f336595d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1846,8 +1846,9 @@ 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);