From 4eedfd4758cd224d2dbd0e321af626b08209e8f9 Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Fri, 29 Mar 2013 16:30:08 +0530 Subject: virtio: console: add locking around c_ovq operations 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(+) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 4b5655109b46..d5ae736ed874 100644 --- 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 ports_device *portdev, u32 port_id, 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(struct virtio_device *vdev) 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, -- cgit v1.2.1