On Fri, Mar 3, 2017 at 7:01 PM, Eric Dumazet <[email protected]> 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 <[email protected]> > Cc: Alexander Duyck <[email protected]> > Cc: Johannes Berg <[email protected]> > Cc: Soheil Hassas Yeganeh <[email protected]> > Cc: Willem de Bruijn <[email protected]>
Acked-by: Soheil Hassas Yeganeh <[email protected]> > --- > 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!
