On Fri, Jan 24, 2025 at 04:30:34PM -0800, Nicolin Chen wrote:
> + list_add_tail(&vevent->node, &eventq->deliver);
> + vevent->on_list = true;
> + vevent->header.sequence = atomic_read(&veventq->sequence);
> + if (atomic_read(&veventq->sequence) == INT_MAX)
> + atomic_set(&veventq->sequence, 0);
> + else
> + atomic_inc(&veventq->sequence);
> + spin_unlock(&eventq->lock);
This is all locked, we don't need veventq->sequence to be an atomic?
The bounding can be done with some simple math:
veventq->sequence = (veventq->sequence + 1) & INT_MAX;
> +static struct iommufd_vevent *
> +iommufd_veventq_deliver_fetch(struct iommufd_veventq *veventq)
> +{
> + struct iommufd_eventq *eventq = &veventq->common;
> + struct list_head *list = &eventq->deliver;
> + struct iommufd_vevent *vevent = NULL;
> +
> + spin_lock(&eventq->lock);
> + if (!list_empty(list)) {
> + vevent = list_first_entry(list, struct iommufd_vevent, node);
> + list_del(&vevent->node);
> + vevent->on_list = false;
> + }
> + /* Make a copy of the overflow node for copy_to_user */
> + if (vevent == &veventq->overflow) {
> + vevent = kzalloc(sizeof(*vevent), GFP_ATOMIC);
> + if (vevent)
> + memcpy(vevent, &veventq->overflow, sizeof(*vevent));
> + }
This error handling is wonky, if we can't allocate then we shouldn't
have done the list_del. Just return NULL which will cause
iommufd_veventq_fops_read() to exist and userspace will try again.
> @@ -403,6 +531,10 @@ static int iommufd_eventq_fops_release(struct inode *inode, struct file *filep)
> {
> struct iommufd_eventq *eventq = filep->private_data;
>
> + if (eventq->obj.type == IOMMUFD_OBJ_VEVENTQ) {
> + atomic_set(&eventq_to_veventq(eventq)->sequence, 0);
> + atomic_set(&eventq_to_veventq(eventq)->num_events, 0);
> + }
Why? We are about to free the memory?
> +int iommufd_veventq_alloc(struct iommufd_ucmd *ucmd)
> +{
> + struct iommu_veventq_alloc *cmd = ucmd->cmd;
> + struct iommufd_veventq *veventq;
> + struct iommufd_viommu *viommu;
> + int fdno;
> + int rc;
> +
> + if (cmd->flags || cmd->type == IOMMU_VEVENTQ_TYPE_DEFAULT)
> + return -EOPNOTSUPP;
> + if (!cmd->veventq_depth)
> + return -EINVAL;
Check __reserved for 0 too
Jason
