4.4-stable review patch. If anyone has any objections, please let me know.
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From: Halil Pasic pasic@linux.ibm.com
commit 2448a299ec416a80f699940a86f4a6d9a4f643b1 upstream.
Currently we have a race on vcdev->config in virtio_ccw_get_config() and in virtio_ccw_set_config().
This normally does not cause problems, as these are usually infrequent operations. However, for some devices writing to/reading from the config space can be triggered through sysfs attributes. For these, userspace can force the race by increasing the frequency.
Signed-off-by: Halil Pasic pasic@linux.ibm.com Cc: stable@vger.kernel.org Message-Id: 20180925121309.58524-2-pasic@linux.ibm.com Signed-off-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/s390/virtio/virtio_ccw.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/drivers/s390/virtio/virtio_ccw.c +++ b/drivers/s390/virtio/virtio_ccw.c @@ -833,6 +833,7 @@ static void virtio_ccw_get_config(struct int ret; struct ccw1 *ccw; void *config_area; + unsigned long flags;
ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL); if (!ccw) @@ -851,11 +852,13 @@ static void virtio_ccw_get_config(struct if (ret) goto out_free;
+ spin_lock_irqsave(&vcdev->lock, flags); memcpy(vcdev->config, config_area, offset + len); - if (buf) - memcpy(buf, &vcdev->config[offset], len); if (vcdev->config_ready < offset + len) vcdev->config_ready = offset + len; + spin_unlock_irqrestore(&vcdev->lock, flags); + if (buf) + memcpy(buf, config_area + offset, len);
out_free: kfree(config_area); @@ -869,6 +872,7 @@ static void virtio_ccw_set_config(struct struct virtio_ccw_device *vcdev = to_vc_device(vdev); struct ccw1 *ccw; void *config_area; + unsigned long flags;
ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL); if (!ccw) @@ -881,9 +885,11 @@ static void virtio_ccw_set_config(struct /* Make sure we don't overwrite fields. */ if (vcdev->config_ready < offset) virtio_ccw_get_config(vdev, 0, NULL, offset); + spin_lock_irqsave(&vcdev->lock, flags); memcpy(&vcdev->config[offset], buf, len); /* Write the config area to the host. */ memcpy(config_area, vcdev->config, sizeof(vcdev->config)); + spin_unlock_irqrestore(&vcdev->lock, flags); ccw->cmd_code = CCW_CMD_WRITE_CONF; ccw->flags = 0; ccw->count = offset + len;