diff options
authorAmit Shah <amit.shah@redhat.com>2013-03-29 16:30:08 +0530
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-11 12:04:18 -0700
commit0e2400e24c096092c7b4cf736160d4e5e9070dec (patch)
parente83f2e8240f4dbc8f2740f9fc999d7bb10351e61 (diff)
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 <xfu@redhat.com> Signed-off-by: Amit Shah <amit.shah@redhat.com> Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com> Reviewed-by: Asias He <asias@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> [wyj: Backported to 3.4: adjust context] Signed-off-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 762737e62b3a..a81f4694f322 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;
@@ -460,11 +461,14 @@ 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, GFP_ATOMIC) >= 0) {
while (!virtqueue_get_buf(vq, &len))
+ spin_unlock(&portdev->c_ovq_lock);
return 0;
@@ -1752,6 +1756,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
unsigned int nr_added_bufs;
+ spin_lock_init(&portdev->c_ovq_lock);
INIT_WORK(&portdev->control_work, &control_work_handler);
nr_added_bufs = fill_queue(portdev->c_ivq,