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

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Message-ID: <20190516050032.ef7cfcjjgwjvm4nv@kafai-mbp>
Date:   Thu, 16 May 2019 05:00:35 +0000
From:   Martin Lau <kafai@...com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>,
        Wei Wang <weiwan@...gle.com>, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net] ipv6: prevent possible fib6 leaks

On Wed, May 15, 2019 at 07:39:52PM -0700, Eric Dumazet wrote:
> 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.
Nice fix!

Acked-by: Martin KaFai Lau <kafai@...com>