On Mon, Sep 28, 2015 at 5:24 PM, Pravin B Shelar <pshe...@nicira.com> wrote:
> Earlier patch 6ae459bda tried to detect void ckecksum partial
> skb by comparing pull length to checksum offset. But it does
> not work for all cases since checksum-offset depends on
> updates to skb->data.
>
> Following patch fixes it by validating checksum start offset
> after skb-data pointer is updated. Negative value of checksum
> offset start means there is no need to checksum.
>
> Fixes: 6ae459bda ("skbuff: Fix skb checksum flag on skb pull")
> Reported-by: Andrew Vagin <ava...@odin.com>
> Signed-off-by: Pravin B Shelar <pshe...@nicira.com>
> ---
> This and 6ae459bda patches needs to be backported to stable.
> ---
> include/linux/skbuff.h | 2 +-
> net/core/skbuff.c | 9 +++++----
> 2 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2b0a30a..4398411 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2708,7 +2708,7 @@ static inline void skb_postpull_rcsum(struct sk_buff
> *skb,
> if (skb->ip_summed == CHECKSUM_COMPLETE)
> skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
> else if (skb->ip_summed == CHECKSUM_PARTIAL &&
> - skb_checksum_start_offset(skb) <= len)
> + skb_checksum_start_offset(skb) < 0)
> skb->ip_summed = CHECKSUM_NONE;
> }
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index dad4dd3..fab4599 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -2958,11 +2958,12 @@ EXPORT_SYMBOL_GPL(skb_append_pagefrags);
> */
> unsigned char * skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
> {
> + unsigned char *data = skb->data;
> +
> BUG_ON(len > skb->len);
> - skb->len -= len;
> - BUG_ON(skb->len < skb->data_len);
> - skb_postpull_rcsum(skb, skb->data, len);
> - return skb->data += len;
> + __skb_pull(skb, len);
> + skb_postpull_rcsum(skb, data, len);
> + return skb->data;
> }
Nice cleanup in skb_pull_rcsum, but does this affect other calls to
skb_postpull_rcsum?
> EXPORT_SYMBOL_GPL(skb_pull_rcsum);
>
> --
> 1.7.1
>
> --
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