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

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Message-Id: <20190430.234014.837178465736820152.davem@davemloft.net>
Date:   Tue, 30 Apr 2019 23:40:14 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        syzkaller@...glegroups.com, dsahern@...il.com
Subject: Re: [PATCH net] ipv6: fix races in ip6_dst_destroy()

From: Eric Dumazet <edumazet@...gle.com>
Date: Sun, 28 Apr 2019 12:22:25 -0700

> 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.
 ...
> Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: David Ahern <dsahern@...il.com>

Applied and queued up for -stable, thanks Eric.