releases/4.14.97/net-fix-usage-of-pskb_trim_rcsum.patch

   1 From foo@baz Sat Jan 26 10:34:35 CET 2019
   2 From: Ross Lagerwall <ross.lagerwall@citrix.com>
   3 Date: Thu, 17 Jan 2019 15:34:38 +0000
   4 Subject: net: Fix usage of pskb_trim_rcsum
   5
   6 From: Ross Lagerwall <ross.lagerwall@citrix.com>
   7
   8 [ Upstream commit 6c57f0458022298e4da1729c67bd33ce41c14e7a ]
   9
  10 In certain cases, pskb_trim_rcsum() may change skb pointers.
  11 Reinitialize header pointers afterwards to avoid potential
  12 use-after-frees. Add a note in the documentation of
  13 pskb_trim_rcsum(). Found by KASAN.
  14
  15 Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
  16 Signed-off-by: David S. Miller <davem@davemloft.net>
  17 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  18 ---
  19  drivers/net/ppp/pppoe.c                  |    1 +
  20  include/linux/skbuff.h                   |    1 +
  21  net/bridge/br_netfilter_ipv6.c           |    1 +
  22  net/bridge/netfilter/nft_reject_bridge.c |    1 +
  23  net/ipv4/ip_input.c                      |    1 +
  24  5 files changed, 5 insertions(+)
  25
  26 --- a/drivers/net/ppp/pppoe.c
  27 +++ b/drivers/net/ppp/pppoe.c
  28 @@ -445,6 +445,7 @@ static int pppoe_rcv(struct sk_buff *skb
  29         if (pskb_trim_rcsum(skb, len))
  30                 goto drop;
  31
  32 +       ph = pppoe_hdr(skb);
  33         pn = pppoe_pernet(dev_net(dev));
  34
  35         /* Note that get_item does a sock_hold(), so sk_pppox(po)
  36 --- a/include/linux/skbuff.h
  37 +++ b/include/linux/skbuff.h
  38 @@ -3163,6 +3163,7 @@ int pskb_trim_rcsum_slow(struct sk_buff
  39   *
  40   *     This is exactly the same as pskb_trim except that it ensures the
  41   *     checksum of received packets are still valid after the operation.
  42 + *     It can change skb pointers.
  43   */
  44
  45  static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
  46 --- a/net/bridge/br_netfilter_ipv6.c
  47 +++ b/net/bridge/br_netfilter_ipv6.c
  48 @@ -131,6 +131,7 @@ int br_validate_ipv6(struct net *net, st
  49                                         IPSTATS_MIB_INDISCARDS);
  50                         goto drop;
  51                 }
  52 +               hdr = ipv6_hdr(skb);
  53         }
  54         if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb))
  55                 goto drop;
  56 --- a/net/bridge/netfilter/nft_reject_bridge.c
  57 +++ b/net/bridge/netfilter/nft_reject_bridge.c
  58 @@ -230,6 +230,7 @@ static bool reject6_br_csum_ok(struct sk
  59             pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
  60                 return false;
  61
  62 +       ip6h = ipv6_hdr(skb);
  63         thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
  64         if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
  65                 return false;
  66 --- a/net/ipv4/ip_input.c
  67 +++ b/net/ipv4/ip_input.c
  68 @@ -481,6 +481,7 @@ int ip_rcv(struct sk_buff *skb, struct n
  69                 goto drop;
  70         }
  71
  72 +       iph = ip_hdr(skb);
  73         skb->transport_header = skb->network_header + iph->ihl*4;
  74
  75         /* Remove any debris in the socket control block */