>From 11fd997d724f520ca628615e7ffbfd7901c40b62 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 6 Feb 2015 13:28:38 +0900
Subject: [PATCH] virtio: Avoid possible kernel panic if DEBUG is enabled.
The virtqueue_add() calls START_USE() upon entry. The virtqueue_kick() is
called if vq->num_added == (1 << 16) - 1 before calling END_USE().
The virtqueue_kick_prepare() called via virtqueue_kick() calls START_USE()
upon entry, and will call panic() if DEBUG is enabled.
Move this virtqueue_kick() call to after END_USE() call.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 00ec6b3..596735b 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -245,14 +245,14 @@ static inline int virtqueue_add(struct virtqueue *_vq,
vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) + 1);
vq->num_added++;
+ pr_debug("Added buffer head %i to %p\n", head, vq);
+ END_USE(vq);
+
/* This is very unlikely, but theoretically possible. Kick
* just in case. */
if (unlikely(vq->num_added == (1 << 16) - 1))
virtqueue_kick(_vq);
- pr_debug("Added buffer head %i to %p\n", head, vq);
- END_USE(vq);
-
return 0;
}
--
1.8.3.1
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