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Mon, 17 Aug 2026 22:47:54 -0700 (PDT) Received: from [127.0.1.1] ([188.253.126.51]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d5bb514bacsm13097505ad.27.2026.08.17.22.47.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 22:47:54 -0700 (PDT) From: Jia Jia To: amit@kernel.org, mst@redhat.com, jasowangio@gmail.com Cc: xuanzhuo@linux.alibaba.com, eperezma@redhat.com, gregkh@linuxfoundation.org, arnd@arndb.de, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] virtio_console: do not free control-out buffers on remove Date: Tue, 18 Aug 2026 13:47:09 +0800 Message-Id: <20260818054709.282196-1-physicalmtea@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit __send_control_msg() publishes &portdev->cpkt as the control-out virtqueue cookie. remove_vqs() walks every virtqueue and passes leftover cookies to free_buf(), which treats them as struct port_buffer and reads sgpages. If a control message is still on c_ovq when the device is unbound, free_buf() reads past the ports_device object. KASAN reported the use through: free_buf remove_vqs virtcons_remove unbind_store Drain c_ovq without freeing. The packet lives in portdev and is released with it. Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset") Cc: stable@vger.kernel.org Signed-off-by: Jia Jia --- drivers/char/virtio_console.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 9a33217c68d9..6e9bf064826e 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1886,10 +1886,24 @@ static void remove_vqs(struct ports_device *portdev) virtio_device_for_each_vq(portdev->vdev, vq) { struct port_buffer *buf; + unsigned int len; - flush_bufs(vq, true); - while ((buf = virtqueue_detach_unused_buf(vq))) - free_buf(buf, true); + /* + * c_ovq cookies are &portdev->cpkt, not port_buffer. + * Detach them but do not free_buf(). + */ + if (vq == portdev->c_ovq) { + spin_lock(&portdev->c_ovq_lock); + while (virtqueue_get_buf(vq, &len)) + ; + while (virtqueue_detach_unused_buf(vq)) + ; + spin_unlock(&portdev->c_ovq_lock); + } else { + flush_bufs(vq, true); + while ((buf = virtqueue_detach_unused_buf(vq))) + free_buf(buf, true); + } cond_resched(); } portdev->vdev->config->del_vqs(portdev->vdev); -- 2.34.1