linux-kernel - Re: [PATCH v2] xfrm: policy: Fix possible user after free in __xfrm_policy

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Message-ID: <20190228064106.v4fe5b2ij3gbodxk@gondor.apana.org.au>
Date:   Thu, 28 Feb 2019 14:41:06 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Yue Haibing <yuehaibing@...wei.com>
Cc:     steffen.klassert@...unet.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] xfrm: policy: Fix possible user after free in
 __xfrm_policy_unlink

On Thu, Feb 28, 2019 at 02:38:01PM +0800, Yue Haibing wrote:
>
> diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
> index a131f9f..aaa45c9 100644
> --- a/net/xfrm/xfrm_user.c
> +++ b/net/xfrm/xfrm_user.c
> @@ -1424,7 +1424,8 @@ static int verify_newpolicy_info(struct xfrm_userpolicy_info *p)
>  	ret = verify_policy_dir(p->dir);
>  	if (ret)
>  		return ret;
> -	if (p->index && ((p->index & XFRM_POLICY_MAX) != p->dir))
> +	if (p->index && (((p->index & XFRM_POLICY_MAX) != p->dir) ||
> +			 (xfrm_policy_id2dir(p->index) >= XFRM_POLICY_MAX)))

Please just check 

	xfrm_policy_id2dir(p->index) != p->dir

Thanks,
-- 
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