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

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Date:   Sun, 28 Apr 2019 16:02:05 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] ipv6: fix races in ip6_dst_destroy()

On 4/28/19 1:22 PM, 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.
> 
...
> 
> 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>
> ---
>  net/ipv6/ip6_fib.c | 4 +---
>  net/ipv6/route.c   | 9 ++-------
>  2 files changed, 3 insertions(+), 10 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...il.com>

Thanks for the fix, Eric.