Commit e2ae7fd4 authored by Halil Pasic's avatar Halil Pasic Committed by Greg Kroah-Hartman

virtio/s390: avoid race on vcdev->config

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: default avatarHalil Pasic <>
Message-Id: <>
Signed-off-by: default avatarCornelia Huck <>
Signed-off-by: default avatarMichael S. Tsirkin <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 92c01d8f
......@@ -833,6 +833,7 @@ static void virtio_ccw_get_config(struct virtio_device *vdev,
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 virtio_device *vdev,
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);
......@@ -869,6 +872,7 @@ static void virtio_ccw_set_config(struct virtio_device *vdev,
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 virtio_device *vdev,
/* 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;
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