linux-kernel - Re: KASAN: use-after-free Read in rtnetlink_put

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Message-Id: <20180801.114636.279269263935333136.davem@davemloft.net>
Date:   Wed, 01 Aug 2018 11:46:36 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     sd@...asysnail.net, eric.dumazet@...il.com,
        syzbot+41f9c04b50ef70c66947@...kaller.appspotmail.com,
        christian.brauner@...ntu.com, dsahern@...il.com, fw@...len.de,
        jbenc@...hat.com, ktkhai@...tuozzo.com,
        linux-kernel@...r.kernel.org, lucien.xin@...il.com,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in rtnetlink_put_metrics

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Tue, 31 Jul 2018 16:03:13 -0700

> Looks like this commit is completely unnecessary,
> fib6_drop_pcpu_from() calls fib6_info_release()
> which calls fib6_info_destroy_rcu(), so this metrics
> will be released twice...

And even if there was a leak here, it's illegal to free this
metrics memory synchronously since it is RCU protected.

That's why it normally goes through fib6_info_destroy_rcu().

Sabrina, I'm going to revert your changes unless I see some
progress here by the end of today.