Re: [PATCH v4 3/6] virt: sevguest: Prep for kernel internal {get, get_ext}_report()

[Kuppuswamy Sathyanarayanan]

On 9/25/2023 9:17 PM, Dan Williams wrote:
> In preparation for using the configs-tsm facility to convey attestation
> blobs to userspace, switch to using the 'sockptr' api for copying
> payloads to provided buffers where 'sockptr' handles user vs kernel
> buffers.
> 
> While configfs-tsm is meant to replace existing confidential computing
> ioctl() implementations for attestation report retrieval the old ioctl()
> path needs to stick around for a deprecation period.
> 
> No behavior change intended.
> 
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Cc: Dionna Glaze <dionnaglaze@xxxxxxxxxx>
> Cc: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

>  drivers/virt/coco/sev-guest/sev-guest.c |   50 ++++++++++++++++++++-----------
>  1 file changed, 33 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 97dbe715e96a..c3c9e9ea691f 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -19,6 +19,7 @@
>  #include <crypto/aead.h>
>  #include <linux/scatterlist.h>
>  #include <linux/psp-sev.h>
> +#include <linux/sockptr.h>
>  #include <uapi/linux/sev-guest.h>
>  #include <uapi/linux/psp-sev.h>
>  
> @@ -470,7 +471,13 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
>  	return 0;
>  }
>  
> -static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +struct snp_req_resp {
> +	sockptr_t req_data;
> +	sockptr_t resp_data;
> +};
> +
> +static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg,
> +		      struct snp_req_resp *io)
>  {
>  	struct snp_guest_crypto *crypto = snp_dev->crypto;
>  	struct snp_report_resp *resp;
> @@ -479,10 +486,10 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
>  
>  	lockdep_assert_held(&snp_cmd_mutex);
>  
> -	if (!arg->req_data || !arg->resp_data)
> +	if (sockptr_is_null(io->req_data) || sockptr_is_null(io->resp_data))
>  		return -EINVAL;
>  
> -	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> +	if (copy_from_sockptr(&req, io->req_data, sizeof(req)))
>  		return -EFAULT;
>  
>  	/*
> @@ -501,7 +508,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
>  	if (rc)
>  		goto e_free;
>  
> -	if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> +	if (copy_to_sockptr(io->resp_data, resp, sizeof(*resp)))
>  		rc = -EFAULT;
>  
>  e_free:
> @@ -550,22 +557,25 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
>  	return rc;
>  }
>  
> -static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg,
> +			  struct snp_req_resp *io)
> +
>  {
>  	struct snp_guest_crypto *crypto = snp_dev->crypto;
>  	struct snp_ext_report_req req;
>  	struct snp_report_resp *resp;
>  	int ret, npages = 0, resp_len;
> +	sockptr_t certs_address;
>  
>  	lockdep_assert_held(&snp_cmd_mutex);
>  
> -	if (!arg->req_data || !arg->resp_data)
> +	if (sockptr_is_null(io->req_data) || sockptr_is_null(io->resp_data))
>  		return -EINVAL;
>  
> -	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> +	if (copy_from_sockptr(&req, io->req_data, sizeof(req)))
>  		return -EFAULT;
>  
> -	/* userspace does not want certificate data */
> +	/* caller does not want certificate data */
>  	if (!req.certs_len || !req.certs_address)
>  		goto cmd;
>  
> @@ -573,8 +583,13 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
>  	    !IS_ALIGNED(req.certs_len, PAGE_SIZE))
>  		return -EINVAL;
>  
> -	if (!access_ok((const void __user *)req.certs_address, req.certs_len))
> -		return -EFAULT;
> +	if (sockptr_is_kernel(io->resp_data)) {
> +		certs_address = KERNEL_SOCKPTR((void *)req.certs_address);
> +	} else {
> +		certs_address = USER_SOCKPTR((void __user *)req.certs_address);
> +		if (!access_ok(certs_address.user, req.certs_len))
> +			return -EFAULT;
> +	}
>  
>  	/*
>  	 * Initialize the intermediate buffer with all zeros. This buffer
> @@ -604,21 +619,19 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
>  	if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
>  		req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
>  
> -		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
> +		if (copy_to_sockptr(io->req_data, &req, sizeof(req)))
>  			ret = -EFAULT;
>  	}
>  
>  	if (ret)
>  		goto e_free;
>  
> -	if (npages &&
> -	    copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
> -			 req.certs_len)) {
> +	if (npages && copy_to_sockptr(certs_address, snp_dev->certs_data, req.certs_len)) {
>  		ret = -EFAULT;
>  		goto e_free;
>  	}
>  
> -	if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> +	if (copy_to_sockptr(io->resp_data, resp, sizeof(*resp)))
>  		ret = -EFAULT;
>  
>  e_free:
> @@ -631,6 +644,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
>  	struct snp_guest_dev *snp_dev = to_snp_dev(file);
>  	void __user *argp = (void __user *)arg;
>  	struct snp_guest_request_ioctl input;
> +	struct snp_req_resp io;
>  	int ret = -ENOTTY;
>  
>  	if (copy_from_user(&input, argp, sizeof(input)))
> @@ -651,15 +665,17 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
>  		return -ENOTTY;
>  	}
>  
> +	io.req_data = USER_SOCKPTR((void __user *)input.req_data);
> +	io.resp_data = USER_SOCKPTR((void __user *)input.resp_data);
>  	switch (ioctl) {
>  	case SNP_GET_REPORT:
> -		ret = get_report(snp_dev, &input);
> +		ret = get_report(snp_dev, &input, &io);
>  		break;
>  	case SNP_GET_DERIVED_KEY:
>  		ret = get_derived_key(snp_dev, &input);
>  		break;
>  	case SNP_GET_EXT_REPORT:
> -		ret = get_ext_report(snp_dev, &input);
> +		ret = get_ext_report(snp_dev, &input, &io);
>  		break;
>  	default:
>  		break;
> 
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer