On 05/03/2018 05:33 PM, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.du...@intel.com>
>
> This patch makes it so that if a destructor is not present we avoid trying
> to update the skb socket or any reference counting that would be associated
> with the NULL socket and/or descriptor. By doing this we can support
> traffic coming from another namespace without any issues.
>
> Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com>
> ---
> net/ipv4/udp_offload.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index fd94bbb369b2..52760660d674 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -195,6 +195,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> unsigned int sum_truesize = 0;
> struct udphdr *uh;
> unsigned int mss;
> + bool copy_dtor;
> __sum16 check;
> __be16 newlen;
>
> @@ -208,12 +209,14 @@ struct sk_buff *__udp_gso_segment(struct sk_buff
> *gso_skb,
> skb_pull(gso_skb, sizeof(*uh));
>
> /* clear destructor to avoid skb_segment assigning it to tail */
> - WARN_ON_ONCE(gso_skb->destructor != sock_wfree);
> + copy_dtor = gso_skb->destructor == sock_wfree;
> + WARN_ON_ONCE(gso_skb->destructor && !copy_dtor);
Why not simply clear gso_skb->destructor only if copy_dtor is true ?
Then we can get rid of this WARN_ON_ONCE()
> gso_skb->destructor = NULL;
>
> segs = skb_segment(gso_skb, features);
> if (unlikely(IS_ERR_OR_NULL(segs))) {
> - gso_skb->destructor = sock_wfree;
> + if (copy_dtor)
> + gso_skb->destructor = sock_wfree;
> return segs;
> }
>
> @@ -234,9 +237,11 @@ struct sk_buff *__udp_gso_segment(struct sk_buff
> *gso_skb,
> (__force u32)newlen));
>
> for (;;) {
> - seg->destructor = sock_wfree;
> - seg->sk = sk;
> - sum_truesize += seg->truesize;
> + if (copy_dtor) {
> + seg->destructor = sock_wfree;
> + seg->sk = sk;
> + sum_truesize += seg->truesize;
> + }
>
> if (!seg->next)
> break;
> @@ -268,7 +273,9 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> uh->check = gso_make_checksum(seg, ~check);
>
> /* update refcount for the packet */
> - refcount_add(sum_truesize - gso_skb->truesize, &sk->sk_wmem_alloc);
> + if (copy_dtor)
> + refcount_add(sum_truesize - gso_skb->truesize,
> + &sk->sk_wmem_alloc);
> out:
> return segs;
> }
>
