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Tue, 18 Aug 2026 19:12:56 -0700 (PDT) Received: from [127.0.1.1] ([188.253.126.51]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc15545da49sm96199a12.13.2026.08.18.19.12.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2026 19:12:56 -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 Subject: [PATCH v2] virtio_console: do not free control-out buffers on remove Date: Wed, 19 Aug 2026 10:12:30 +0800 Message-Id: <20260819021230.292696-1-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 slab-out-of-bounds in free_buf(): free_buf remove_vqs virtcons_remove unbind_store The object was the ports_device allocated in virtcons_probe(). Drain c_ovq without freeing. The packet lives in portdev and is released with it. Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset") Signed-off-by: Jia Jia --- Changes in v2: - Guard c_ovq handling with use_multiport() because c_ovq and c_ovq_lock are only initialized for multiport devices. drivers/char/virtio_console.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 9a33217c68d9..8e0d10d91763 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1884,12 +1884,27 @@ static const struct file_operations portdev_fops = { static void remove_vqs(struct ports_device *portdev) { struct virtqueue *vq; + bool multiport = use_multiport(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 (multiport && 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