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authorJason Wang <jasowang@redhat.com>2022-06-22 03:29:40 +0200
committerMichael S. Tsirkin <mst@redhat.com>2022-06-24 08:49:48 +0200
commitc346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163 (patch)
tree4e3a09595a5ec554cf002679c587049c627fba49
parentvirtio: Remove unnecessary variable assignments (diff)
downloadlinux-c346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163.tar.xz
linux-c346dae4f3fbce51bbd4f2ec5e8c6f9b91e93163.zip
virtio: disable notification hardening by default
We try to harden virtio device notifications in 8b4ec69d7e09 ("virtio: harden vring IRQ"). It works with the assumption that the driver or core can properly call virtio_device_ready() at the right place. Unfortunately, this seems to be not true and uncover various bugs of the existing drivers, mainly the issue of using virtio_device_ready() incorrectly. So let's add a Kconfig option and disable it by default. It gives us time to fix the drivers and then we can consider re-enabling it. Signed-off-by: Jason Wang <jasowang@redhat.com> Message-Id: <20220622012940.21441-1-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
-rw-r--r--drivers/s390/virtio/virtio_ccw.c9
-rw-r--r--drivers/virtio/Kconfig13
-rw-r--r--drivers/virtio/virtio.c2
-rw-r--r--drivers/virtio/virtio_ring.c12
-rw-r--r--include/linux/virtio_config.h2
5 files changed, 37 insertions, 1 deletions
diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index 97e51c34e6cf..161d3b141f0d 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -1136,8 +1136,13 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
vcdev->err = -EIO;
}
virtio_ccw_check_activity(vcdev, activity);
- /* Interrupts are disabled here */
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+ /*
+ * Paired with virtio_ccw_synchronize_cbs() and interrupts are
+ * disabled here.
+ */
read_lock(&vcdev->irq_lock);
+#endif
for_each_set_bit(i, indicators(vcdev),
sizeof(*indicators(vcdev)) * BITS_PER_BYTE) {
/* The bit clear must happen before the vring kick. */
@@ -1146,7 +1151,9 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
vq = virtio_ccw_vq_by_ind(vcdev, i);
vring_interrupt(0, vq);
}
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
read_unlock(&vcdev->irq_lock);
+#endif
if (test_bit(0, indicators2(vcdev))) {
virtio_config_changed(&vcdev->vdev);
clear_bit(0, indicators2(vcdev));
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index a6dc8b5846fe..e1556d2a355a 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -29,6 +29,19 @@ menuconfig VIRTIO_MENU
if VIRTIO_MENU
+config VIRTIO_HARDEN_NOTIFICATION
+ bool "Harden virtio notification"
+ help
+ Enable this to harden the device notifications and suppress
+ those that happen at a time where notifications are illegal.
+
+ Experimental: Note that several drivers still have bugs that
+ may cause crashes or hangs when correct handling of
+ notifications is enforced; depending on the subset of
+ drivers and devices you use, this may or may not work.
+
+ If unsure, say N.
+
config VIRTIO_PCI
tristate "PCI driver for virtio devices"
depends on PCI
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 6bace84ae37e..7deeed30d1f3 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -219,6 +219,7 @@ static int virtio_features_ok(struct virtio_device *dev)
* */
void virtio_reset_device(struct virtio_device *dev)
{
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
/*
* The below virtio_synchronize_cbs() guarantees that any
* interrupt for this line arriving after
@@ -227,6 +228,7 @@ void virtio_reset_device(struct virtio_device *dev)
*/
virtio_break_device(dev);
virtio_synchronize_cbs(dev);
+#endif
dev->config->reset(dev);
}
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index ef30465dd39c..96731cdef422 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1708,7 +1708,11 @@ static struct virtqueue *vring_create_virtqueue_packed(
vq->we_own_ring = true;
vq->notify = notify;
vq->weak_barriers = weak_barriers;
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
vq->broken = true;
+#else
+ vq->broken = false;
+#endif
vq->last_used_idx = 0 | (1 << VRING_PACKED_EVENT_F_WRAP_CTR);
vq->event_triggered = false;
vq->num_added = 0;
@@ -2154,9 +2158,13 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
}
if (unlikely(vq->broken)) {
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
dev_warn_once(&vq->vq.vdev->dev,
"virtio vring IRQ raised before DRIVER_OK");
return IRQ_NONE;
+#else
+ return IRQ_HANDLED;
+#endif
}
/* Just a hint for performance: so it's ok that this can be racy! */
@@ -2199,7 +2207,11 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
vq->we_own_ring = false;
vq->notify = notify;
vq->weak_barriers = weak_barriers;
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
vq->broken = true;
+#else
+ vq->broken = false;
+#endif
vq->last_used_idx = 0;
vq->event_triggered = false;
vq->num_added = 0;
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 49c7c32815f1..b47c2e7ed0ee 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -257,6 +257,7 @@ void virtio_device_ready(struct virtio_device *dev)
WARN_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
/*
* The virtio_synchronize_cbs() makes sure vring_interrupt()
* will see the driver specific setup if it sees vq->broken
@@ -264,6 +265,7 @@ void virtio_device_ready(struct virtio_device *dev)
*/
virtio_synchronize_cbs(dev);
__virtio_unbreak_device(dev);
+#endif
/*
* The transport should ensure the visibility of vq->broken
* before setting DRIVER_OK. See the comments for the transport