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Tue, 15 Sep 2026 09:33:02 -0700 (PDT) Received: from leonardi-redhat ([151.29.41.106]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e83dba8f4sm1920305e9.13.2026.09.15.09.33.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 09:33:02 -0700 (PDT) Date: Tue, 15 Sep 2026 18:32:59 +0200 From: Luigi Leonardi To: Aldo Ariel Panzardo Cc: Stefano Garzarella , virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] vsock: ignore empty child namespace mode writes Message-ID: References: <20260915111417.2726515-1-qwe.aldo@gmail.com> <20260915141547.3010692-1-qwe.aldo@gmail.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260915141547.3010692-1-qwe.aldo@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Wt0e6e4ZxcYf9IQS-DLEfvriUAy4D7SllCMcnTRTk9E_1789489983 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline Hi Aldo, On Tue, Sep 15, 2026 at 11:15:47AM -0300, Aldo Ariel Panzardo wrote: >__vsock_net_mode_string() returns success without updating new_mode when >the transfer length is zero. Its caller then reads the uninitialized enum >and may permanently store a stack-derived value in the write-once child >mode. > >Return before inspecting or storing new_mode when no bytes were >transferred. This also prevents an empty write from locking the current >mode. > >Fixes: eafb64f40ca4 ("vsock: add netns to vsock core") >Cc: stable@vger.kernel.org >Signed-off-by: Aldo Ariel Panzardo >--- > net/vmw_vsock/af_vsock.c | 2 ++ > 1 file changed, 2 insertions(+) > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >index 622dbd0467..816d25b314 100644 >--- a/net/vmw_vsock/af_vsock.c >+++ b/net/vmw_vsock/af_vsock.c >@@ -2883,6 +2883,8 @@ static int vsock_net_child_mode_string(const struct ctl_table *table, int write, > vsock_net_child_mode(net), &new_mode); > if (ret) > return ret; >+ if (!*lenp) >+ return 0; > > if (write) { > /* Prevent a "local" namespace from escalating to "global", >-- >2.43.0 > Code LGTM. Reviewed-by: Luigi Leonardi To reproduce it, I suppose we need a kernel that does not come with `CONFIG_INIT_STACK_ALL_ZERO` set. @Stefano do you think it's worth adding a test for this case? Just out of curiosity, how did you find this bug? Thanks, Luigi