From: Herbert Xu <herbert@gondor.apana.org.au>
To: Zhuoliang Zhang <zhuoliang.zhang@mediatek.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>,
wsd_upstream@mediatek.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] net: xfrm: fix a race condition during allocing spi
Date: Wed, 21 Oct 2020 18:12:22 +1100 [thread overview]
Message-ID: <20201021071222.GA11474@gondor.apana.org.au> (raw)
In-Reply-To: <20201020081800.29454-1-zhuoliang.zhang@mediatek.com>
On Tue, Oct 20, 2020 at 04:18:00PM +0800, Zhuoliang Zhang wrote:
> From: zhuoliang zhang <zhuoliang.zhang@mediatek.com>
>
> we found that the following race condition exists in
> xfrm_alloc_userspi flow:
>
> user thread state_hash_work thread
> ---- ----
> xfrm_alloc_userspi()
> __find_acq_core()
> /*alloc new xfrm_state:x*/
> xfrm_state_alloc()
> /*schedule state_hash_work thread*/
> xfrm_hash_grow_check() xfrm_hash_resize()
> xfrm_alloc_spi /*hold lock*/
> x->id.spi = htonl(spi) spin_lock_bh(&net->xfrm.xfrm_state_lock)
> /*waiting lock release*/ xfrm_hash_transfer()
> spin_lock_bh(&net->xfrm.xfrm_state_lock) /*add x into hlist:net->xfrm.state_byspi*/
> hlist_add_head_rcu(&x->byspi)
> spin_unlock_bh(&net->xfrm.xfrm_state_lock)
>
> /*add x into hlist:net->xfrm.state_byspi 2 times*/
> hlist_add_head_rcu(&x->byspi)
>
> So the same xfrm_stame (x) is added into the same list_hash
> (net->xfrm.state_byspi)2 times that makes the list_hash become
> a inifite loop.
Your explanation makes no sense. Prior to obtaining the spin lock
on the LHS, the state x hasn't been added to thte table yet. So
how can the RHS be transferring it?
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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next prev parent reply other threads:[~2020-10-21 7:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 8:18 [PATCH] net: xfrm: fix a race condition during allocing spi Zhuoliang Zhang
2020-10-21 7:12 ` Herbert Xu [this message]
2020-10-22 5:53 ` zhuoliang.zhang
2020-10-22 6:48 ` Herbert Xu
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