On Fri, Mar 3, 2017 at 7:01 PM, Eric Dumazet <eduma...@google.com> wrote:
>
> TX skbs do not necessarily hold a reference on skb->sk->sk_refcnt
> By the time TX completion happens, sk_refcnt might be already 0.
>
> sock_hold()/sock_put() would then corrupt critical state, like
> sk_wmem_alloc and lead to leaks or use after free.
>
> Fixes: 62bccb8cdb69 ("net-timestamp: Make the clone operation stand-alone
> from phy timestamping")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Cc: Alexander Duyck <alexander.h.du...@intel.com>
> Cc: Johannes Berg <johan...@sipsolutions.net>
> Cc: Soheil Hassas Yeganeh <soh...@google.com>
> Cc: Willem de Bruijn <will...@google.com>
Acked-by: Soheil Hassas Yeganeh <soh...@google.com>
> ---
> net/core/skbuff.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index
> e2f37a560ec43ccf60a71f190423bd265eccf594..cd4ba8c6b6091651403cf74de8c60ccf69aa3e7b
> 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3828,13 +3828,14 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
> if (!skb_may_tx_timestamp(sk, false))
> return;
>
> - /* take a reference to prevent skb_orphan() from freeing the socket */
> - sock_hold(sk);
> -
> - *skb_hwtstamps(skb) = *hwtstamps;
> - __skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);
> -
> - sock_put(sk);
> + /* Take a reference to prevent skb_orphan() from freeing the socket,
> + * but only if the socket refcount is not zero.
> + */
> + if (likely(atomic_inc_not_zero(&sk->sk_refcnt))) {
> + *skb_hwtstamps(skb) = *hwtstamps;
> + __skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);
> + sock_put(sk);
> + }
> }
> EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
>
> --
> 2.12.0.rc1.440.g5b76565f74-goog
>
Thanks for the fix!
