netdev - Re: [PATCH net] ipv6: prevent possible fib6 leaks

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Message-Id: <20190516.122549.1356146859638469688.davem@davemloft.net>
Date:   Thu, 16 May 2019 12:25:49 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        syzkaller@...glegroups.com, weiwan@...gle.com, dsahern@...il.com,
        kafai@...com
Subject: Re: [PATCH net] ipv6: prevent possible fib6 leaks

From: Eric Dumazet <edumazet@...gle.com>
Date: Wed, 15 May 2019 19:39:52 -0700

> At ipv6 route dismantle, fib6_drop_pcpu_from() is responsible
> for finding all percpu routes and set their ->from pointer
> to NULL, so that fib6_ref can reach its expected value (1).
> 
> The problem right now is that other cpus can still catch the
> route being deleted, since there is no rcu grace period
> between the route deletion and call to fib6_drop_pcpu_from()
> 
> This can leak the fib6 and associated resources, since no
> notifier will take care of removing the last reference(s).
> 
> I decided to add another boolean (fib6_destroying) instead
> of reusing/renaming exception_bucket_flushed to ease stable backports,
> and properly document the memory barriers used to implement this fix.
> 
> This patch has been co-developped with Wei Wang.
> 
> Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable.