netdev - Re: [PATCH net] ipv6: fix races in ip6_dst

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Message-ID: <20190429155227.etjcgwss6vqgutss@kafai-mbp.dhcp.thefacebook.com>
Date:   Mon, 29 Apr 2019 15:52:29 +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>,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net] ipv6: fix races in ip6_dst_destroy()

On Sun, Apr 28, 2019 at 12:22:25PM -0700, Eric Dumazet wrote:
> We had many syzbot reports that seem to be caused by use-after-free
> of struct fib6_info.
> 
> ip6_dst_destroy(), fib6_drop_pcpu_from() and rt6_remove_exception()
> are writers vs rt->from, and use non consistent synchronization among
> themselves.
> 
> Switching to xchg() will solve the issues with no possible
> lockdep issues.
Acked-by: Martin KaFai Lau <kafai@...com>