linux-kernel - Re: [PATCH v2] xfrm: policy: Fix doulbe free in xfrm_policy

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Message-ID: <20200323062914.GA5811@gondor.apana.org.au>
Date:   Mon, 23 Mar 2020 17:29:14 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     steffen.klassert@...unet.com, davem@...emloft.net, kuba@...nel.org,
        timo.teras@....fi, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] xfrm: policy: Fix doulbe free in xfrm_policy_timer

On Mon, Mar 23, 2020 at 09:41:55AM +0800, YueHaibing wrote:
>
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index dbda08ec566e..ae0689174bbf 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -434,6 +434,7 @@ EXPORT_SYMBOL(xfrm_policy_destroy);
>  
>  static void xfrm_policy_kill(struct xfrm_policy *policy)
>  {
> +	write_lock_bh(&policy->lock);
>  	policy->walk.dead = 1;
>  
>  	atomic_inc(&policy->genid);
> @@ -445,6 +446,7 @@ static void xfrm_policy_kill(struct xfrm_policy *policy)
>  	if (del_timer(&policy->timer))
>  		xfrm_pol_put(policy);
>  
> +	write_unlock_bh(&policy->lock);

Why did you expand the critical section? Can't you just undo the
patch in xfrm_policy_kill?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt