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Tue, 21 Apr 2026 12:44:42 -0700 (PDT) Message-ID: <676ac55c-1549-40a7-9a0c-c69e472417e1@gmail.com> Date: Tue, 21 Apr 2026 12:44:24 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: yuantan098@gmail.com, netdev@vger.kernel.org, idosch@mellanox.com, dsahern@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, jiri@resnulli.us, yifanwucs@gmail.com, tomapufckgml@gmail.com, bird@lzu.edu.cn, royenheart@gmail.com Subject: Re: [PATCH net v3 1/1] net: l3mdev: Reject non-L3 uppers in slave helpers To: Ido Schimmel , Ren Wei References: <20260419145332.3988923-1-n05ec@lzu.edu.cn> <20260420113208.GA972415@shredder> <20260420182640.GA1027405@shredder> <20260421091039.GA1085009@shredder> From: Yuan Tan In-Reply-To: <20260421091039.GA1085009@shredder> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/21/2026 2:10 AM, Ido Schimmel wrote: > On Mon, Apr 20, 2026 at 09:26:50PM +0300, Ido Schimmel wrote: >> On Mon, Apr 20, 2026 at 02:32:08PM +0300, Ido Schimmel wrote: >>> On Sun, Apr 19, 2026 at 10:53:32PM +0800, Ren Wei wrote: >>>> From: Haoze Xie >>>> >>>> Several l3mdev slave-side helpers resolve an upper device and then use >>>> l3mdev_ops without first proving that the resolved device is still a >>>> valid L3 master. >>>> >>>> During slave transition, an RCU reader can transiently observe an upper >>>> that is not an L3 master. Guard the affected slave-resolved paths by >>>> requiring the resolved upper to still be an L3 master before using >>>> l3mdev_ops, while keeping existing L3 RX handler providers intact. >>>> >>>> Fixes: fdeea7be88b1 ("net: vrf: Set slave's private flag before linking") >>>> Cc: stable@kernel.org >>>> Reported-by: Yifan Wu >>>> Reported-by: Juefei Pu >>>> Co-developed-by: Yuan Tan >>>> Signed-off-by: Yuan Tan >>>> Suggested-by: Xin Liu >>>> Tested-by: Haoze Xie >>>> Signed-off-by: Haoze Xie >>>> Signed-off-by: Ao Zhou >>> I think it's fine for net: >>> >>> Reviewed-by: Ido Schimmel >> Thought about this again. I would like to check another approach >> (synchronize_net() after clearing IFF_L3MDEV_SLAVE). Will update >> tomorrow. > Sorry about the back and forth, but I thought about it again last night > and I think that this is a better fix: > > https://github.com/idosch/linux/commit/e67517758ebcddf8a1b97817e4ab0fbf82f467fe.patch > > It's a minimal fix in the control plane of the VRF driver which doesn't > add more checks in the data path. I can submit it later this week unless > there are objections. Thank for you time and review! Btw could you add a Reported-by: Yuan Tan ? Thanks.