From: Jason Wang jasowang@redhat.com
This patch will check the weight and exit the loop if we exceeds the weight. This is useful for preventing scsi kthread from hogging cpu which is guest triggerable.
This addresses CVE-2019-3900.
[upstream c1ea02f15ab5efb3e93fc3144d895410bf79fcf2 Balbir - backport to stable 4.14 ] Cc: Paolo Bonzini pbonzini@redhat.com Cc: Stefan Hajnoczi stefanha@redhat.com Fixes: 057cbf49a1f0 ("tcm_vhost: Initial merge for vhost level target fabric driver") Signed-off-by: Jason Wang jasowang@redhat.com Signed-off-by: Balbir Singh sblbir@amzn.com --- drivers/vhost/scsi.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c index 0abb7cbf54b7..cb4ab5b955ad 100644 --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -846,7 +846,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq) u64 tag; u32 exp_data_len, data_direction; unsigned int out = 0, in = 0; - int head, ret, prot_bytes; + int head, ret, prot_bytes, c = 0; size_t req_size, rsp_size = sizeof(struct virtio_scsi_cmd_resp); size_t out_size, in_size; u16 lun; @@ -865,7 +865,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
vhost_disable_notify(&vs->dev, vq);
- for (;;) { + do { head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, NULL, NULL); @@ -1080,7 +1080,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq) */ INIT_WORK(&cmd->work, vhost_scsi_submission_work); queue_work(vhost_scsi_workqueue, &cmd->work); - } + } while (likely(!vhost_exceeds_weight(vq, ++c, 0))); out: mutex_unlock(&vq->mutex); }