linux-kernel - Re: [PATCH v2] xfrm: xfrm_policy: fix a possible double xfrm_pols_put() in xfrm_bundle

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Message-ID: <20220604074001.GL680067@gauss3.secunet.de>
Date:   Sat, 4 Jun 2022 09:40:01 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Hangyu Hua <hbh25y@...il.com>
CC:     <herbert@...dor.apana.org.au>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <timo.teras@....fi>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] xfrm: xfrm_policy: fix a possible double
 xfrm_pols_put() in xfrm_bundle_lookup()

On Wed, Jun 01, 2022 at 02:46:25PM +0800, Hangyu Hua wrote:
> xfrm_policy_lookup() will call xfrm_pol_hold_rcu() to get a refcount of
> pols[0]. This refcount can be dropped in xfrm_expand_policies() when
> xfrm_expand_policies() return error. pols[0]'s refcount is balanced in
> here. But xfrm_bundle_lookup() will also call xfrm_pols_put() with
> num_pols == 1 to drop this refcount when xfrm_expand_policies() return
> error.
> 
> This patch also fix an illegal address access. pols[0] will save a error
> point when xfrm_policy_lookup fails. This lead to xfrm_pols_put to resolve
> an illegal address in xfrm_bundle_lookup's error path.
> 
> Fix these by setting num_pols = 0 in xfrm_expand_policies()'s error path.
> 
> Fixes: 80c802f3073e ("xfrm: cache bundles instead of policies for outgoing flows")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>

Applied, thanks!