From: Jason Wang <[email protected]> commit c1ea02f15ab5efb3e93fc3144d895410bf79fcf2 upstream.
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. Cc: Paolo Bonzini <[email protected]> Cc: Stefan Hajnoczi <[email protected]> Fixes: 057cbf49a1f0 ("tcm_vhost: Initial merge for vhost level target fabric driver") Signed-off-by: Jason Wang <[email protected]> Reviewed-by: Stefan Hajnoczi <[email protected]> Signed-off-by: Michael S. Tsirkin <[email protected]> Reviewed-by: Stefan Hajnoczi <[email protected]> [bwh: Backported to 4.9: - Drop changes in vhost_scsi_ctl_handle_vq() - Adjust context] Signed-off-by: Ben Hutchings <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/vhost/scsi.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -851,7 +851,7 @@ vhost_scsi_handle_vq(struct vhost_scsi * u64 tag; u32 exp_data_len, data_direction; unsigned out, in; - 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; @@ -870,7 +870,7 @@ vhost_scsi_handle_vq(struct vhost_scsi * vhost_disable_notify(&vs->dev, vq); - for (;;) { + do { head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov), &out, &in, NULL, NULL); @@ -1086,7 +1086,7 @@ vhost_scsi_handle_vq(struct vhost_scsi * */ 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); }
