| Message ID | 20170412232435.80455-1-willemdebruijn.kernel@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com> Date: Wed, 12 Apr 2017 19:24:35 -0400 > From: Willem de Bruijn <willemb@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 <andreyknvl@google.com> > Signed-off-by: Willem de Bruijn <willemb@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.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 9f781092fda9..35c1e2460206 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3807,6 +3807,7 @@ static void __skb_complete_tx_timestamp(struct sk_buff *skb, serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING; serr->ee.ee_info = tstype; serr->opt_stats = opt_stats; + serr->header.h4.iif = skb->dev ? skb->dev->ifindex : 0; if (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID) { serr->ee.ee_data = skb_shinfo(skb)->tskey; if (sk->sk_protocol == IPPROTO_TCP && diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index ebd953bc5607..35076792caa5 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -488,16 +488,15 @@ static bool ipv4_datagram_support_cmsg(const struct sock *sk, return false; /* Support IP_PKTINFO on tstamp packets if requested, to correlate - * timestamp with egress dev. Not possible for packets without dev + * timestamp with egress dev. Not possible for packets without iif * or without payload (SOF_TIMESTAMPING_OPT_TSONLY). */ - if ((!(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_CMSG)) || - (!skb->dev)) + info = PKTINFO_SKB_CB(skb); + if (!(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_CMSG) || + !info->ipi_ifindex) return false; - info = PKTINFO_SKB_CB(skb); info->ipi_spec_dst.s_addr = ip_hdr(skb)->saddr; - info->ipi_ifindex = skb->dev->ifindex; return true; } diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c index eec27f87efac..e011122ebd43 100644 --- a/net/ipv6/datagram.c +++ b/net/ipv6/datagram.c @@ -405,9 +405,6 @@ static inline bool ipv6_datagram_support_addr(struct sock_exterr_skb *serr) * At one point, excluding local errors was a quick test to identify icmp/icmp6 * errors. This is no longer true, but the test remained, so the v6 stack, * unlike v4, also honors cmsg requests on all wifi and timestamp errors. - * - * Timestamp code paths do not initialize the fields expected by cmsg: - * the PKTINFO fields in skb->cb[]. Fill those in here. */ static bool ip6_datagram_support_cmsg(struct sk_buff *skb, struct sock_exterr_skb *serr) @@ -419,14 +416,9 @@ static bool ip6_datagram_support_cmsg(struct sk_buff *skb, if (serr->ee.ee_origin == SO_EE_ORIGIN_LOCAL) return false; - if (!skb->dev) + if (!IP6CB(skb)->iif) return false; - if (skb->protocol == htons(ETH_P_IPV6)) - IP6CB(skb)->iif = skb->dev->ifindex; - else - PKTINFO_SKB_CB(skb)->ipi_ifindex = skb->dev->ifindex; - return true; }