Re: [PATCH v9 13/27] gunyah: vm_mgr: Add/remove user memory regions

[Srivatsa Vaddagiri]

* Elliot Berman <quic_eberman@xxxxxxxxxxx> [2023-01-20 14:46:12]:

> +	/* Check for overlap */
> +	list_for_each_entry(tmp_mapping, &ghvm->memory_mappings, list) {
> +		if (!((mapping->guest_phys_addr + (mapping->npages << PAGE_SHIFT) <=
> +			tmp_mapping->guest_phys_addr) ||
> +			(mapping->guest_phys_addr >=
> +			tmp_mapping->guest_phys_addr + (tmp_mapping->npages << PAGE_SHIFT)))) {
> +			ret = -EEXIST;
> +			goto unlock;
> +		}
> +	}
> +
> +	list_add(&mapping->list, &ghvm->memory_mappings);

I think the potential race condition described last time is still possible. Pls
check.

> +unlock:
> +	mutex_unlock(&ghvm->mm_lock);
> +	if (ret)
> +		goto free_mapping;
> +
> +	mapping->pages = kcalloc(mapping->npages, sizeof(*mapping->pages), GFP_KERNEL);
> +	if (!mapping->pages) {
> +		ret = -ENOMEM;
> +		goto reclaim;

Same comment as last time. Can you check this error path? We seem to call
unpin_user_page() in this path, which is not correct.

> +	}
> +
> +	pinned = pin_user_pages_fast(region->userspace_addr, mapping->npages,
> +					FOLL_WRITE | FOLL_LONGTERM, mapping->pages);
> +	if (pinned < 0) {
> +		ret = pinned;
> +		goto reclaim;

Same comment as above.