queue-5.0/route-avoid-crash-from-dereferencing-null-rt-from.patch

   1 From foo@baz Sat Apr 20 16:43:09 CEST 2019
   2 From: Jonathan Lemon <jonathan.lemon@gmail.com>
   3 Date: Sun, 14 Apr 2019 14:21:29 -0700
   4 Subject: route: Avoid crash from dereferencing NULL rt->from
   5
   6 From: Jonathan Lemon <jonathan.lemon@gmail.com>
   7
   8 [ Upstream commit 9c69a13205151c0d801de9f9d83a818e6e8f60ec ]
   9
  10 When __ip6_rt_update_pmtu() is called, rt->from is RCU dereferenced, but is
  11 never checked for null - rt6_flush_exceptions() may have removed the entry.
  12
  13 [ 1913.989004] RIP: 0010:ip6_rt_cache_alloc+0x13/0x170
  14 [ 1914.209410] Call Trace:
  15 [ 1914.214798]  <IRQ>
  16 [ 1914.219226]  __ip6_rt_update_pmtu+0xb0/0x190
  17 [ 1914.228649]  ip6_tnl_xmit+0x2c2/0x970 [ip6_tunnel]
  18 [ 1914.239223]  ? ip6_tnl_parse_tlv_enc_lim+0x32/0x1a0 [ip6_tunnel]
  19 [ 1914.252489]  ? __gre6_xmit+0x148/0x530 [ip6_gre]
  20 [ 1914.262678]  ip6gre_tunnel_xmit+0x17e/0x3c7 [ip6_gre]
  21 [ 1914.273831]  dev_hard_start_xmit+0x8d/0x1f0
  22 [ 1914.283061]  sch_direct_xmit+0xfa/0x230
  23 [ 1914.291521]  __qdisc_run+0x154/0x4b0
  24 [ 1914.299407]  net_tx_action+0x10e/0x1f0
  25 [ 1914.307678]  __do_softirq+0xca/0x297
  26 [ 1914.315567]  irq_exit+0x96/0xa0
  27 [ 1914.322494]  smp_apic_timer_interrupt+0x68/0x130
  28 [ 1914.332683]  apic_timer_interrupt+0xf/0x20
  29 [ 1914.341721]  </IRQ>
  30
  31 Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected")
  32 Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
  33 Reviewed-by: Eric Dumazet <edumazet@google.com>
  34 Reviewed-by: David Ahern <dsahern@gmail.com>
  35 Reviewed-by: Martin KaFai Lau <kafai@fb.com>
  36 Signed-off-by: David S. Miller <davem@davemloft.net>
  37 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  38 ---
  39  net/ipv6/route.c |    4 ++++
  40  1 file changed, 4 insertions(+)
  41
  42 --- a/net/ipv6/route.c
  43 +++ b/net/ipv6/route.c
  44 @@ -2336,6 +2336,10 @@ static void __ip6_rt_update_pmtu(struct
  45
  46                 rcu_read_lock();
  47                 from = rcu_dereference(rt6->from);
  48 +               if (!from) {
  49 +                       rcu_read_unlock();
  50 +                       return;
  51 +               }
  52                 nrt6 = ip6_rt_cache_alloc(from, daddr, saddr);
  53                 if (nrt6) {
  54                         rt6_do_update_pmtu(nrt6, mtu);