From 9c69a13205151c0d801de9f9d83a818e6e8f60ec Mon Sep 17 00:00:00 2001 From: Jonathan Lemon Date: Sun, 14 Apr 2019 14:21:29 -0700 Subject: [PATCH] route: Avoid crash from dereferencing NULL rt->from When __ip6_rt_update_pmtu() is called, rt->from is RCU dereferenced, but is never checked for null - rt6_flush_exceptions() may have removed the entry. [ 1913.989004] RIP: 0010:ip6_rt_cache_alloc+0x13/0x170 [ 1914.209410] Call Trace: [ 1914.214798] [ 1914.219226] __ip6_rt_update_pmtu+0xb0/0x190 [ 1914.228649] ip6_tnl_xmit+0x2c2/0x970 [ip6_tunnel] [ 1914.239223] ? ip6_tnl_parse_tlv_enc_lim+0x32/0x1a0 [ip6_tunnel] [ 1914.252489] ? __gre6_xmit+0x148/0x530 [ip6_gre] [ 1914.262678] ip6gre_tunnel_xmit+0x17e/0x3c7 [ip6_gre] [ 1914.273831] dev_hard_start_xmit+0x8d/0x1f0 [ 1914.283061] sch_direct_xmit+0xfa/0x230 [ 1914.291521] __qdisc_run+0x154/0x4b0 [ 1914.299407] net_tx_action+0x10e/0x1f0 [ 1914.307678] __do_softirq+0xca/0x297 [ 1914.315567] irq_exit+0x96/0xa0 [ 1914.322494] smp_apic_timer_interrupt+0x68/0x130 [ 1914.332683] apic_timer_interrupt+0xf/0x20 [ 1914.341721] Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected") Signed-off-by: Jonathan Lemon Reviewed-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Martin KaFai Lau Signed-off-by: David S. Miller --- net/ipv6/route.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 0302e0eb07af..7178e32eb15d 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -2330,6 +2330,10 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk, rcu_read_lock(); from = rcu_dereference(rt6->from); + if (!from) { + rcu_read_unlock(); + return; + } nrt6 = ip6_rt_cache_alloc(from, daddr, saddr); if (nrt6) { rt6_do_update_pmtu(nrt6, mtu); -- 2.39.5