Re: [PATCH v4 11/18] nitro_enclaves: Add logic for enclave memory region set

[Alexander Graf]

On 22.06.20 22:03, Andra Paraschiv wrote:
> Another resource that is being set for an enclave is memory. User space
> memory regions, that need to be backed by contiguous memory regions,
> are associated with the enclave.
>
> One solution for allocating / reserving contiguous memory regions, that
> is used for integration, is hugetlbfs. The user space process that is
> associated with the enclave passes to the driver these memory regions.
>
> The enclave memory regions need to be from the same NUMA node as the
> enclave CPUs.
>
> Add ioctl command logic for setting user space memory region for an
> enclave.
>
> Signed-off-by: Alexandru Vasile <lexnv@xxxxxxxxxx>
> Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> ---
> Changelog
>
> v3 -> v4
>
> * Check enclave memory regions are from the same NUMA node as the
>    enclave CPUs.
> * Use dev_err instead of custom NE log pattern.
> * Update the NE ioctl call to match the decoupling from the KVM API.
>
> v2 -> v3
>
> * Remove the WARN_ON calls.
> * Update static calls sanity checks.
> * Update kzfree() calls to kfree().
>
> v1 -> v2
>
> * Add log pattern for NE.
> * Update goto labels to match their purpose.
> * Remove the BUG_ON calls.
> * Check if enclave max memory regions is reached when setting an enclave
>    memory region.
> * Check if enclave state is init when setting an enclave memory region.
> ---
>   drivers/virt/nitro_enclaves/ne_misc_dev.c | 257 ++++++++++++++++++++++
>   1 file changed, 257 insertions(+)
>
> diff --git a/drivers/virt/nitro_enclaves/ne_misc_dev.c b/drivers/virt/nitro_enclaves/ne_misc_dev.c
> index cfdefa52ed2a..17ccb6cdbd75 100644
> --- a/drivers/virt/nitro_enclaves/ne_misc_dev.c
> +++ b/drivers/virt/nitro_enclaves/ne_misc_dev.c
> @@ -476,6 +476,233 @@ static int ne_create_vcpu_ioctl(struct ne_enclave *ne_enclave, u32 vcpu_id)
>   	return rc;
>   }
>   
> +/**
> + * ne_sanity_check_user_mem_region - Sanity check the userspace memory
> + * region received during the set user memory region ioctl call.
> + *
> + * This function gets called with the ne_enclave mutex held.
> + *
> + * @ne_enclave: private data associated with the current enclave.
> + * @mem_region: user space memory region to be sanity checked.
> + *
> + * @returns: 0 on success, negative return value on failure.
> + */
> +static int ne_sanity_check_user_mem_region(struct ne_enclave *ne_enclave,
> +	struct ne_user_memory_region *mem_region)
> +{
> +	if (ne_enclave->mm != current->mm)
> +		return -EIO;
> +
> +	if ((mem_region->memory_size % NE_MIN_MEM_REGION_SIZE) != 0) {
> +		dev_err_ratelimited(ne_misc_dev.this_device,
> +				    "Mem size not multiple of 2 MiB\n");
> +
> +		return -EINVAL;

Can we make this an error that gets propagated to user space explicitly? 
I'd rather have a clear error return value of this function than a 
random message in dmesg.

> +	}
> +
> +	if ((mem_region->userspace_addr & (NE_MIN_MEM_REGION_SIZE - 1)) ||

This logic already relies on the fact that NE_MIN_MEM_REGION_SIZE is a 
power of two. Can you do the same above on the memory_size check?

> +	    !access_ok((void __user *)(unsigned long)mem_region->userspace_addr,
> +		       mem_region->memory_size)) {
> +		dev_err_ratelimited(ne_misc_dev.this_device,
> +				    "Invalid user space addr range\n");
> +
> +		return -EINVAL;

Same comment again. Return different errors for different conditions, so 
that user space has a chance to print proper errors to its users.

Also, don't we have to check alignment of userspace_addr as well?

> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * ne_set_user_memory_region_ioctl - Add user space memory region to the slot
> + * associated with the current enclave.
> + *
> + * This function gets called with the ne_enclave mutex held.
> + *
> + * @ne_enclave: private data associated with the current enclave.
> + * @mem_region: user space memory region to be associated with the given slot.
> + *
> + * @returns: 0 on success, negative return value on failure.
> + */
> +static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
> +	struct ne_user_memory_region *mem_region)
> +{
> +	struct ne_pci_dev_cmd_reply cmd_reply = {};
> +	long gup_rc = 0;
> +	unsigned long i = 0;
> +	struct ne_mem_region *ne_mem_region = NULL;
> +	unsigned long nr_phys_contig_mem_regions = 0;
> +	unsigned long nr_pinned_pages = 0;
> +	struct page **phys_contig_mem_regions = NULL;
> +	int rc = -EINVAL;
> +	struct slot_add_mem_req slot_add_mem_req = {};
> +
> +	rc = ne_sanity_check_user_mem_region(ne_enclave, mem_region);
> +	if (rc < 0)
> +		return rc;
> +
> +	ne_mem_region = kzalloc(sizeof(*ne_mem_region), GFP_KERNEL);
> +	if (!ne_mem_region)
> +		return -ENOMEM;
> +
> +	/*
> +	 * TODO: Update nr_pages value to handle contiguous virtual address
> +	 * ranges mapped to non-contiguous physical regions. Hugetlbfs can give
> +	 * 2 MiB / 1 GiB contiguous physical regions.
> +	 */
> +	ne_mem_region->nr_pages = mem_region->memory_size /
> +		NE_MIN_MEM_REGION_SIZE;
> +
> +	ne_mem_region->pages = kcalloc(ne_mem_region->nr_pages,
> +				       sizeof(*ne_mem_region->pages),
> +				       GFP_KERNEL);
> +	if (!ne_mem_region->pages) {
> +		kfree(ne_mem_region);
> +
> +		return -ENOMEM;

kfree(NULL) is a nop, so you can just set rc and goto free_mem_region 
here and below.

> +	}
> +
> +	phys_contig_mem_regions = kcalloc(ne_mem_region->nr_pages,
> +					  sizeof(*phys_contig_mem_regions),
> +					  GFP_KERNEL);
> +	if (!phys_contig_mem_regions) {
> +		kfree(ne_mem_region->pages);
> +		kfree(ne_mem_region);
> +
> +		return -ENOMEM;
> +	}
> +
> +	/*
> +	 * TODO: Handle non-contiguous memory regions received from user space.
> +	 * Hugetlbfs can give 2 MiB / 1 GiB contiguous physical regions. The
> +	 * virtual address space can be seen as contiguous, although it is
> +	 * mapped underneath to 2 MiB / 1 GiB physical regions e.g. 8 MiB
> +	 * virtual address space mapped to 4 physically contiguous regions of 2
> +	 * MiB.
> +	 */
> +	do {
> +		unsigned long tmp_nr_pages = ne_mem_region->nr_pages -
> +			nr_pinned_pages;
> +		struct page **tmp_pages = ne_mem_region->pages +
> +			nr_pinned_pages;
> +		u64 tmp_userspace_addr = mem_region->userspace_addr +
> +			nr_pinned_pages * NE_MIN_MEM_REGION_SIZE;
> +
> +		gup_rc = get_user_pages(tmp_userspace_addr, tmp_nr_pages,
> +					FOLL_GET, tmp_pages, NULL);
> +		if (gup_rc < 0) {
> +			rc = gup_rc;
> +
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Error in gup [rc=%d]\n", rc);
> +
> +			unpin_user_pages(ne_mem_region->pages, nr_pinned_pages);
> +
> +			goto free_mem_region;
> +		}
> +
> +		nr_pinned_pages += gup_rc;
> +
> +	} while (nr_pinned_pages < ne_mem_region->nr_pages);

Can this deadlock the kernel? Shouldn't we rather return an error when 
we can't pin all pages?

> +
> +	/*
> +	 * TODO: Update checks once physically contiguous regions are collected
> +	 * based on the user space address and get_user_pages() results.
> +	 */
> +	for (i = 0; i < ne_mem_region->nr_pages; i++) {
> +		if (!PageHuge(ne_mem_region->pages[i])) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Not a hugetlbfs page\n");
> +
> +			goto unpin_pages;
> +		}
> +
> +		if (huge_page_size(page_hstate(ne_mem_region->pages[i])) !=
> +		    NE_MIN_MEM_REGION_SIZE) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Page size isn't 2 MiB\n");

Why is a huge page size of >2MB a problem? Can't we just make 
huge_page_size() the ne mem slot size?

> +
> +			goto unpin_pages;
> +		}
> +
> +		if (ne_enclave->numa_node !=
> +		    page_to_nid(ne_mem_region->pages[i])) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Page isn't from NUMA node %d\n",
> +					    ne_enclave->numa_node);
> +
> +			goto unpin_pages;

Is there a way to give user space hints on *why* things are going wrong?

> +		}
> +
> +		/*
> +		 * TODO: Update once handled non-contiguous memory regions
> +		 * received from user space.
> +		 */
> +		phys_contig_mem_regions[i] = ne_mem_region->pages[i];
> +	}
> +
> +	/*
> +	 * TODO: Update once handled non-contiguous memory regions received
> +	 * from user space.
> +	 */
> +	nr_phys_contig_mem_regions = ne_mem_region->nr_pages;
> +
> +	if ((ne_enclave->nr_mem_regions + nr_phys_contig_mem_regions) >
> +	    ne_enclave->max_mem_regions) {
> +		dev_err_ratelimited(ne_misc_dev.this_device,
> +				    "Reached max memory regions %lld\n",
> +				    ne_enclave->max_mem_regions);
> +
> +		goto unpin_pages;
> +	}
> +
> +	for (i = 0; i < nr_phys_contig_mem_regions; i++) {
> +		u64 phys_addr = page_to_phys(phys_contig_mem_regions[i]);
> +
> +		slot_add_mem_req.slot_uid = ne_enclave->slot_uid;
> +		slot_add_mem_req.paddr = phys_addr;
> +		/*
> +		 * TODO: Update memory size of physical contiguous memory
> +		 * region, in case of non-contiguous memory regions received
> +		 * from user space.
> +		 */
> +		slot_add_mem_req.size = NE_MIN_MEM_REGION_SIZE;

Yeah, for now, just make it huge_page_size()! :)

> +
> +		rc = ne_do_request(ne_enclave->pdev, SLOT_ADD_MEM,
> +				   &slot_add_mem_req, sizeof(slot_add_mem_req),
> +				   &cmd_reply, sizeof(cmd_reply));
> +		if (rc < 0) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Error in slot add mem [rc=%d]\n",
> +					    rc);
> +
> +			/* TODO: Only unpin memory regions not added. */

Are we sure we're not creating an unusable system here?

> +			goto unpin_pages;
> +		}
> +
> +		ne_enclave->mem_size += slot_add_mem_req.size;
> +		ne_enclave->nr_mem_regions++;
> +
> +		memset(&slot_add_mem_req, 0, sizeof(slot_add_mem_req));
> +		memset(&cmd_reply, 0, sizeof(cmd_reply));

If you define the variables in the for loop scope, you don't need to 
manually zero them again.


Alex

> +	}
> +
> +	list_add(&ne_mem_region->mem_region_list_entry,
> +		 &ne_enclave->mem_regions_list);
> +
> +	kfree(phys_contig_mem_regions);
> +
> +	return 0;
> +
> +unpin_pages:
> +	unpin_user_pages(ne_mem_region->pages, ne_mem_region->nr_pages);
> +free_mem_region:
> +	kfree(phys_contig_mem_regions);
> +	kfree(ne_mem_region->pages);
> +	kfree(ne_mem_region);
> +
> +	return rc;
> +}
> +
>   static long ne_enclave_ioctl(struct file *file, unsigned int cmd,
>   			     unsigned long arg)
>   {
> @@ -561,6 +788,36 @@ static long ne_enclave_ioctl(struct file *file, unsigned int cmd,
>   		return 0;
>   	}
>   
> +	case NE_SET_USER_MEMORY_REGION: {
> +		struct ne_user_memory_region mem_region = {};
> +		int rc = -EINVAL;
> +
> +		if (copy_from_user(&mem_region, (void *)arg,
> +				   sizeof(mem_region))) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Error in copy from user\n");
> +
> +			return -EFAULT;
> +		}
> +
> +		mutex_lock(&ne_enclave->enclave_info_mutex);
> +
> +		if (ne_enclave->state != NE_STATE_INIT) {
> +			dev_err_ratelimited(ne_misc_dev.this_device,
> +					    "Enclave isn't in init state\n");
> +
> +			mutex_unlock(&ne_enclave->enclave_info_mutex);
> +
> +			return -EINVAL;
> +		}
> +
> +		rc = ne_set_user_memory_region_ioctl(ne_enclave, &mem_region);
> +
> +		mutex_unlock(&ne_enclave->enclave_info_mutex);
> +
> +		return rc;
> +	}
> +
>   	default:
>   		return -ENOTTY;
>   	}



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