releases/5.0.6/ipv6-make-ip6_create_rt_rcu-return-ip6_null_entry-instead-of-null.patch

   1 From foo@baz Thu Mar 28 21:53:58 CET 2019
   2 From: Xin Long <lucien.xin@gmail.com>
   3 Date: Wed, 20 Mar 2019 14:45:48 +0800
   4 Subject: ipv6: make ip6_create_rt_rcu return ip6_null_entry instead of NULL
   5
   6 From: Xin Long <lucien.xin@gmail.com>
   7
   8 [ Upstream commit 1c87e79a002f6a159396138cd3f3ab554a2a8887 ]
   9
  10 Jianlin reported a crash:
  11
  12   [  381.484332] BUG: unable to handle kernel NULL pointer dereference at 0000000000000068
  13   [  381.619802] RIP: 0010:fib6_rule_lookup+0xa3/0x160
  14   [  382.009615] Call Trace:
  15   [  382.020762]  <IRQ>
  16   [  382.030174]  ip6_route_redirect.isra.52+0xc9/0xf0
  17   [  382.050984]  ip6_redirect+0xb6/0xf0
  18   [  382.066731]  icmpv6_notify+0xca/0x190
  19   [  382.083185]  ndisc_redirect_rcv+0x10f/0x160
  20   [  382.102569]  ndisc_rcv+0xfb/0x100
  21   [  382.117725]  icmpv6_rcv+0x3f2/0x520
  22   [  382.133637]  ip6_input_finish+0xbf/0x460
  23   [  382.151634]  ip6_input+0x3b/0xb0
  24   [  382.166097]  ipv6_rcv+0x378/0x4e0
  25
  26 It was caused by the lookup function __ip6_route_redirect() returns NULL in
  27 fib6_rule_lookup() when ip6_create_rt_rcu() returns NULL.
  28
  29 So we fix it by simply making ip6_create_rt_rcu() return ip6_null_entry
  30 instead of NULL.
  31
  32 v1->v2:
  33   - move down 'fallback:' to make it more readable.
  34
  35 Fixes: e873e4b9cc7e ("ipv6: use fib6_info_hold_safe() when necessary")
  36 Reported-by: Jianlin Shi <jishi@redhat.com>
  37 Suggested-by: Paolo Abeni <pabeni@redhat.com>
  38 Signed-off-by: Xin Long <lucien.xin@gmail.com>
  39 Reviewed-by: David Ahern <dsahern@gmail.com>
  40 Acked-by: Wei Wang <weiwan@google.com>
  41 Signed-off-by: David S. Miller <davem@davemloft.net>
  42 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  43 ---
  44  net/ipv6/route.c |   18 ++++++++++--------
  45  1 file changed, 10 insertions(+), 8 deletions(-)
  46
  47 --- a/net/ipv6/route.c
  48 +++ b/net/ipv6/route.c
  49 @@ -1040,14 +1040,20 @@ static struct rt6_info *ip6_create_rt_rc
  50         struct rt6_info *nrt;
  51
  52         if (!fib6_info_hold_safe(rt))
  53 -               return NULL;
  54 +               goto fallback;
  55
  56         nrt = ip6_dst_alloc(dev_net(dev), dev, flags);
  57 -       if (nrt)
  58 -               ip6_rt_copy_init(nrt, rt);
  59 -       else
  60 +       if (!nrt) {
  61                 fib6_info_release(rt);
  62 +               goto fallback;
  63 +       }
  64 +
  65 +       ip6_rt_copy_init(nrt, rt);
  66 +       return nrt;
  67
  68 +fallback:
  69 +       nrt = dev_net(dev)->ipv6.ip6_null_entry;
  70 +       dst_hold(&nrt->dst);
  71         return nrt;
  72  }
  73
  74 @@ -1096,10 +1102,6 @@ restart:
  75                 dst_hold(&rt->dst);
  76         } else {
  77                 rt = ip6_create_rt_rcu(f6i);
  78 -               if (!rt) {
  79 -                       rt = net->ipv6.ip6_null_entry;
  80 -                       dst_hold(&rt->dst);
  81 -               }
  82         }
  83
  84         rcu_read_unlock();