From: Rusty Russell on
From: "Michael S. Tsirkin" <mst(a)redhat.com>

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(a)oracle.com>
Signed-off-by: Michael S. Tsirkin <mst(a)redhat.com>
Signed-off-by: Rusty Russell <rusty(a)rustcorp.com.au>
Tested-by: Chris Mason <chris.mason(a)oracle.com>
Cc: stable(a)kernel.org # .34.x
---
drivers/virtio/virtio_ring.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index dd35b34..bffec32 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -164,7 +164,8 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq,
gfp_t gfp)
{
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);

@@ -174,8 +175,8 @@ int virtqueue_add_buf_gfp(struct virtqueue *_vq,
* 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, gfp);
- if (head != vq->vring.num)
+ if (likely(head >= 0))
goto add_head;
}

BUG_ON(out + in > vq->vring.num);
--
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