From: Willem de Bruijn <willemdebruijn.ker...@gmail.com> Date: Wed, 12 Apr 2017 19:24:35 -0400
> From: Willem de Bruijn <will...@google.com> > > Syzkaller reported a use-after-free in ip_recv_error at line > > info->ipi_ifindex = skb->dev->ifindex; > > This function is called on dequeue from the error queue, at which > point the device pointer may no longer be valid. > > Save ifindex on enqueue in __skb_complete_tx_timestamp, when the > pointer is valid or NULL. Store it in temporary storage skb->cb. > > It is safe to reference skb->dev here, as called from device drivers > or dev_queue_xmit. The exception is when called from tcp_ack_tstamp; > in that case it is NULL and ifindex is set to 0 (invalid). > > Do not return a pktinfo cmsg if ifindex is 0. This maintains the > current behavior of not returning a cmsg if skb->dev was NULL. > > On dequeue, the ipv4 path will cast from sock_exterr_skb to > in_pktinfo. Both have ifindex as their first element, so no explicit > conversion is needed. This is by design, introduced in commit > 0b922b7a829c ("net: original ingress device index in PKTINFO"). For > ipv6 ip6_datagram_support_cmsg converts to in6_pktinfo. > > Fixes: 829ae9d61165 ("net-timestamp: allow reading recv cmsg on errqueue with > origin tstamp") > > Reported-by: Andrey Konovalov <andreyk...@google.com> > Signed-off-by: Willem de Bruijn <will...@google.com> Applied and queued up for -stable, thanks. In the future please don't insert empty lines between the Fixes: and other tags. Thanks.