From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934821Ab3DGXjL (ORCPT ); Sun, 7 Apr 2013 19:39:11 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46699 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934646Ab3DGX3j (ORCPT ); Sun, 7 Apr 2013 19:29:39 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Wanlong Gao" , "Rusty Russell" , "FuXiangChun" , "Amit Shah" , "Asias He" Date: Sun, 07 Apr 2013 23:45:42 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [42/74] virtio: console: add locking around c_ovq operations In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:b4b3:7e2a:e2d0:3478 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.43-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Amit Shah commit 9ba5c80b1aea8648a3efe5f22dc1f7cacdfbeeb8 upstream. When multiple ovq operations are being performed (lots of open/close operations on virtio_console fds), the __send_control_msg() function can get confused without locking. A simple recipe to cause badness is: * create a QEMU VM with two virtio-serial ports * in the guest, do while true;do echo abc >/dev/vport0p1;done while true;do echo edf >/dev/vport0p2;done In one run, this caused a panic in __send_control_msg(). In another, I got virtio_console virtio0: control-o:id 0 is not a head! This also results repeated messages similar to these on the host: qemu-kvm: virtio-serial-bus: Unexpected port id 478762112 for device virtio-serial-bus.0 qemu-kvm: virtio-serial-bus: Unexpected port id 478762368 for device virtio-serial-bus.0 Reported-by: FuXiangChun Signed-off-by: Amit Shah Reviewed-by: Wanlong Gao Reviewed-by: Asias He Signed-off-by: Rusty Russell [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/char/virtio_console.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -132,6 +132,7 @@ struct ports_device { /* To protect the vq operations for the control channel */ spinlock_t c_ivq_lock; + spinlock_t c_ovq_lock; /* The current config space is stored here */ struct virtio_console_config config; @@ -457,11 +458,14 @@ static ssize_t __send_control_msg(struct vq = portdev->c_ovq; sg_init_one(sg, &cpkt, sizeof(cpkt)); + + spin_lock(&portdev->c_ovq_lock); if (virtqueue_add_buf(vq, sg, 1, 0, &cpkt) >= 0) { virtqueue_kick(vq); while (!virtqueue_get_buf(vq, &len)) cpu_relax(); } + spin_unlock(&portdev->c_ovq_lock); return 0; } @@ -1722,6 +1726,7 @@ static int __devinit virtcons_probe(stru unsigned int nr_added_bufs; spin_lock_init(&portdev->c_ivq_lock); + spin_lock_init(&portdev->c_ovq_lock); INIT_WORK(&portdev->control_work, &control_work_handler); nr_added_bufs = fill_queue(portdev->c_ivq,