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To:     jonathan.lemon@gmail.com
Cc:     netdev@vger.kernel.org, dsahern@gmail.com, kernel-team@fb.com
Subject: Re: [PATCH net] route: Avoid crash from dereferencing NULL rt->from
From:   David Miller <davem@davemloft.net>
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From: Jonathan Lemon <jonathan.lemon@gmail.com>
Date: Sun, 14 Apr 2019 14:21:29 -0700

> 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.lemon@gmail.com>

Applied with Fixes: tag added, and queued up for -stable.

Thanks.