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Thu, 12 Nov 2026 09:42:35 -0800 (PST) Received: from [10.67.48.245] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2edb6d4b12esm37630625ad.21.2026.11.12.09.42.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Nov 2026 09:42:33 -0800 (PST) Message-ID: Date: Thu, 12 Nov 2026 09:42:32 -0800 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] vlan: prevent cross-netns MII register writes To: Andrew Lunn , Jakub Kicinski Cc: Hungyu Lin , davem@davemloft.net, edumazet@kernel.org, pabeni@redhat.com, horms@kernel.org, n05ec@lzu.edu.cn, ylong030@ucr.edu, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261106124639.12584-1-dennylin0707@gmail.com> <20261112075624.23c04230@kernel.org> <706b09ea-49cc-4801-a24b-b22d2ea7d257@lunn.ch> Content-Language: en-US, fr-FR From: Florian Fainelli In-Reply-To: <706b09ea-49cc-4801-a24b-b22d2ea7d257@lunn.ch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/12/26 08:15, Andrew Lunn wrote: > On Thu, Nov 12, 2026 at 07:56:24AM -0800, Jakub Kicinski wrote: >> On Fri, 6 Nov 2026 12:46:39 +0000 Hungyu Lin wrote: >>> vlan_dev_ioctl() forwards SIOCSMIIREG to the underlying real >>> device without checking whether the VLAN device and real device >>> belong to the same network namespace. >>> >>> A VLAN device can be moved into another network namespace while >>> its real device remains in the host namespace. This allows a >>> process with the required privileges in the VLAN device's >>> namespace to modify PHY registers on the host's real device. >>> >>> Reject SIOCSMIIREG when the two devices belong to different >>> network namespaces. Preserve MII reads across namespaces and >>> allow MII writes when both devices belong to the same namespace. >>> >>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Hungyu Lin >> >>> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c >>> index bca0a3693636..0d0904103302 100644 >>> --- a/net/8021q/vlan_dev.c >>> +++ b/net/8021q/vlan_dev.c >>> @@ -416,9 +416,12 @@ static int vlan_dev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd) >>> ifrr.ifr_ifru = ifr->ifr_ifru; >>> >>> switch (cmd) { >>> + case SIOCSMIIREG: >>> + if (!net_eq(dev_net(dev), dev_net(real_dev))) >>> + break; >>> + fallthrough; >>> case SIOCGMIIPHY: >>> case SIOCGMIIREG: >>> - case SIOCSMIIREG: >>> err = dev_eth_ioctl(real_dev, &ifrr, cmd); >>> break; >>> } >> >> Andrew, Florian, any idea if we could delete this completely? >> Why would anyone want to run MII/PHY commands on a VLAN? > > It does seem questionable. Agreed, it does not quite make sense to me to forward these ioctl() calls. Looks like this predates the import of Linux-2.6.12-rc2 into git, need to do some more history digging to find out why this was done. > > Hungyu, do any other virtual devices forward these ioctl calls to the > physical device below? I assume they have the same problem. So we need > a fix for them all. > > Andrew -- Florian