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Subject[106/205] virtio: fix oops on OOM
2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Michael S. Tsirkin <mst@redhat.com>

commit 1fe9b6fef11771461e69ecd1bc8935a1c7c90cb5 upstream.

virtio ring was changed to return an error code on OOM,
but one caller was missed and still checks for vq->vring.num.
The fix is just to check for <0 error code.

Long term it might make sense to change goto add_head to
just return an error on oom instead, but let's apply
a minimal fix for 2.6.35.

Reported-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/virtio/virtio_ring.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -162,7 +162,8 @@ static int vring_add_buf(struct virtqueu
void *data)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- unsigned int i, avail, head, uninitialized_var(prev);
+ unsigned int i, avail, uninitialized_var(prev);
+ int head;

START_USE(vq);

@@ -172,7 +173,7 @@ static int vring_add_buf(struct virtqueu
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && (out + in) > 1 && vq->num_free) {
head = vring_add_indirect(vq, sg, out, in);
- if (head != vq->vring.num)
+ if (likely(head >= 0))
goto add_head;
}




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