netdev - Re: [PATCH net] xfrm6: fix inet6_dev refcount underflow problem

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Date: Mon, 25 Sep 2023 07:41:24 +0200
From: Steffen Klassert <steffen.klassert@...unet.com>
To: Zhang Changzhong <zhangchangzhong@...wei.com>
CC: Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller"
	<davem@...emloft.net>, David Ahern <dsahern@...nel.org>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Xin Long <lucien.xin@...il.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] xfrm6: fix inet6_dev refcount underflow problem

On Fri, Sep 15, 2023 at 07:20:41PM +0800, Zhang Changzhong wrote:
> There are race conditions that may lead to inet6_dev refcount underflow
> in xfrm6_dst_destroy() and rt6_uncached_list_flush_dev().
> 
> One of the refcount underflow bugs is shown below:
> 	(cpu 1)                	|	(cpu 2)
> xfrm6_dst_destroy()             |
>   ...                           |
>   in6_dev_put()                 |
> 				|  rt6_uncached_list_flush_dev()
>   ...				|    ...
> 				|    in6_dev_put()
>   rt6_uncached_list_del()       |    ...
>   ...                           |
> 
> xfrm6_dst_destroy() calls rt6_uncached_list_del() after in6_dev_put(),
> so rt6_uncached_list_flush_dev() has a chance to call in6_dev_put()
> again for the same inet6_dev.
> 
> Fix it by moving in6_dev_put() after rt6_uncached_list_del() in
> xfrm6_dst_destroy().
> 
> Fixes: 510c321b5571 ("xfrm: reuse uncached_list to track xdsts")
> Signed-off-by: Zhang Changzhong <zhangchangzhong@...wei.com>

Applied, thanks a lot!