| From foo@baz Fri Nov 2 10:04:04 CET 2018 |
| From: Dimitris Michailidis <dmichail@google.com> |
| Date: Fri, 19 Oct 2018 17:07:13 -0700 |
| Subject: net: fix pskb_trim_rcsum_slow() with odd trim offset |
| |
| From: Dimitris Michailidis <dmichail@google.com> |
| |
| [ Upstream commit d55bef5059dd057bd077155375c581b49d25be7e ] |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/core/skbuff.c | 5 +++-- |
| 1 file changed, 3 insertions(+), 2 deletions(-) |
| |
| --- a/net/core/skbuff.c |
| +++ b/net/core/skbuff.c |
| @@ -1585,8 +1585,9 @@ int pskb_trim_rcsum_slow(struct sk_buff |
| 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); |
| } |