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[79.53.30.11]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e83d9fae9sm3560385e9.6.2026.09.15.09.57.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 09:57:20 -0700 (PDT) Date: Tue, 15 Sep 2026 18:57:15 +0200 From: Stefano Garzarella To: Luigi Leonardi Cc: Aldo Ariel Panzardo , 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: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Tue, Sep 15, 2026 at 06:32:59PM +0200, Luigi Leonardi wrote: >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? Not a strong opinion on this on my side. Thanks, Stefano > >Just out of curiosity, how did you find this bug? > >Thanks, >Luigi >