| From foo@baz Sat Apr 29 08:22:13 CEST 2017 |
| From: Willem de Bruijn <willemb@google.com> |
| Date: Wed, 12 Apr 2017 19:24:35 -0400 |
| Subject: net-timestamp: avoid use-after-free in ip_recv_error |
| |
| From: Willem de Bruijn <willemb@google.com> |
| |
| |
| [ Upstream commit 1862d6208db0aeca9c8ace44915b08d5ab2cd667 ] |
| |
| 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> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/core/skbuff.c | 1 + |
| net/ipv4/ip_sockglue.c | 9 ++++----- |
| net/ipv6/datagram.c | 10 +--------- |
| 3 files changed, 6 insertions(+), 14 deletions(-) |
| |
| --- a/net/core/skbuff.c |
| +++ b/net/core/skbuff.c |
| @@ -3779,6 +3779,7 @@ static void __skb_complete_tx_timestamp( |
| serr->ee.ee_errno = ENOMSG; |
| serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING; |
| serr->ee.ee_info = tstype; |
| + 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 && |
| --- a/net/ipv4/ip_sockglue.c |
| +++ b/net/ipv4/ip_sockglue.c |
| @@ -474,16 +474,15 @@ static bool ipv4_datagram_support_cmsg(c |
| 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; |
| } |
| |
| --- a/net/ipv6/datagram.c |
| +++ b/net/ipv6/datagram.c |
| @@ -400,9 +400,6 @@ static inline bool ipv6_datagram_support |
| * 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) |
| @@ -414,14 +411,9 @@ static bool ip6_datagram_support_cmsg(st |
| 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; |
| } |
| |