netdev - Re: [PATCH net] ipv6: take rcu lock in rawv6_send

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Message-Id: <20181005.144629.1332596138050709254.davem@davemloft.net>
Date:   Fri, 05 Oct 2018 14:46:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     weiwan@...gle.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH net] ipv6: take rcu lock in rawv6_send_hdrinc()

From: Wei Wang <weiwan@...gle.com>
Date: Thu,  4 Oct 2018 10:12:37 -0700

> From: Wei Wang <weiwan@...gle.com>
> 
> In rawv6_send_hdrinc(), in order to avoid an extra dst_hold(), we
> directly assign the dst to skb and set passed in dst to NULL to avoid
> double free.
> However, in error case, we free skb and then do stats update with the
> dst pointer passed in. This causes use-after-free on the dst.
> Fix it by taking rcu read lock right before dst could get released to
> make sure dst does not get freed until the stats update is done.
> Note: we don't have this issue in ipv4 cause dst is not used for stats
> update in v4.
> 
> Syzkaller reported following crash:
 ...
> Fixes: 1789a640f556 ("raw: avoid two atomics in xmit")
> Signed-off-by: Wei Wang <weiwan@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com> 

Applied and queued up for -stable, thanks.