On 4/14/19 3:21 PM, Jonathan Lemon wrote:
> 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] <IRQ>
> [ 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] </IRQ>
>
> Signed-off-by: Jonathan Lemon <jonathan.le...@gmail.com>
> ---
> net/ipv6/route.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index d555edaaff13..b9cbe6815f2c 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2331,6 +2331,10 @@ 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);
>
Thanks for the fix.
Reviewed-by: David Ahern <dsah...@gmail.com>
