On 10/29/2018 05:35 PM, Cong Wang wrote:
> Most callers of pskb_trim_rcsum() simply drops the skb when
> it fails, however, ip_check_defrag() still continues to pass
> the skb up to stack. In that case, we should restore its previous
> csum if __pskb_trim() fails.
>
> Found this during code review.
>
> Fixes: 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are
> friends")
> Cc: Eric Dumazet <eduma...@google.com>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
> ---
> net/core/skbuff.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 946de0e24c87..5decd6e6d2b6 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -1843,6 +1843,9 @@ EXPORT_SYMBOL(___pskb_trim);
> */
> int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
> {
> + __wsum old_csum = skb->csum;
> + int ret;
> +
> if (skb->ip_summed == CHECKSUM_COMPLETE) {
> int delta = skb->len - len;
>
> @@ -1850,7 +1853,10 @@ int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned
> int len)
> skb_checksum(skb, len, delta, 0),
> len);
> }
> - return __pskb_trim(skb, len);
> + ret = __pskb_trim(skb, len);
> + if (unlikely(ret))
> + skb->csum = old_csum;
Would not it be simpler to set ip_summed to CHECKSUM_NONE (no need to save
old_csum) ?
> + return ret;
> }
> EXPORT_SYMBOL(pskb_trim_rcsum_slow);
>
>
