Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2] netfilter: xt_owner: Add supplementary groups option
To:     Lukasz Pawelczyk <l.pawelczyk@samsung.com>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
        Florian Westphal <fw@strlen.de>,
        "David S. Miller" <davem@davemloft.net>,
        netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Lukasz Pawelczyk <havner@gmail.com>
References: <CGME20190508141219eucas1p1e5a899714747b497499976113ea9681f@eucas1p1.samsung.com>
 <20190508141211.4191-1-l.pawelczyk@samsung.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <98f71c64-3887-b715-effb-894224a71ef9@gmail.com>
Date:   Wed, 8 May 2019 07:58:25 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <20190508141211.4191-1-l.pawelczyk@samsung.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 5/8/19 10:12 AM, Lukasz Pawelczyk wrote:
> The XT_SUPPL_GROUPS flag causes GIDs specified with XT_OWNER_GID to
> be also checked in the supplementary groups of a process.
> 
> Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@samsung.com>
> ---
>  include/uapi/linux/netfilter/xt_owner.h |  1 +
>  net/netfilter/xt_owner.c                | 23 ++++++++++++++++++++---
>  2 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/netfilter/xt_owner.h b/include/uapi/linux/netfilter/xt_owner.h
> index fa3ad84957d5..d646f0dc3466 100644
> --- a/include/uapi/linux/netfilter/xt_owner.h
> +++ b/include/uapi/linux/netfilter/xt_owner.h
> @@ -8,6 +8,7 @@ enum {
>  	XT_OWNER_UID    = 1 << 0,
>  	XT_OWNER_GID    = 1 << 1,
>  	XT_OWNER_SOCKET = 1 << 2,
> +	XT_SUPPL_GROUPS = 1 << 3,
>  };
>  
>  struct xt_owner_match_info {
> diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c
> index 46686fb73784..283a1fb5cc52 100644
> --- a/net/netfilter/xt_owner.c
> +++ b/net/netfilter/xt_owner.c
> @@ -91,11 +91,28 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
>  	}
>  
>  	if (info->match & XT_OWNER_GID) {
> +		unsigned int i, match = false;
>  		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
>  		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
> -		if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
> -		     gid_lte(filp->f_cred->fsgid, gid_max)) ^
> -		    !(info->invert & XT_OWNER_GID))
> +		struct group_info *gi = filp->f_cred->group_info;
> +
> +		if (gid_gte(filp->f_cred->fsgid, gid_min) &&
> +		    gid_lte(filp->f_cred->fsgid, gid_max))
> +			match = true;
> +
> +		if (!match && (info->match & XT_SUPPL_GROUPS) && gi) {
> +			for (i = 0; i < gi->ngroups; ++i) {
> +				kgid_t group = gi->gid[i];
> +
> +				if (gid_gte(group, gid_min) &&
> +				    gid_lte(group, gid_max)) {
> +					match = true;
> +					break;
> +				}
> +			}
> +		}
> +
> +		if (match ^ !(info->invert & XT_OWNER_GID))
>  			return false;
>  	}
>  
> 

How can this be safe on SMP ?