virt: sevguest: Prep for kernel internal get_ext_report()

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@alien8.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Dionna Glaze <dionnaglaze@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 5bee58ef5f1e3977da39335bce6865d926dc381e..e5f8f115f4aff6a807e612a0b17d48c8bf891dc5 100644 (file)
--- 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>
 
@@ -475,6 +476,11 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
        return 0;
 }
 
+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_guest_crypto *crypto = snp_dev->crypto;
@@ -555,22 +561,25 @@ 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_ext_report_req *req = &snp_dev->req.ext_report;
        struct snp_guest_crypto *crypto = snp_dev->crypto;
        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;
 
@@ -578,8 +587,13 @@ 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
@@ -609,21 +623,19 @@ 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:
@@ -636,6 +648,7 @@ 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)))
@@ -664,7 +677,14 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
                ret = get_derived_key(snp_dev, &input);
                break;
        case SNP_GET_EXT_REPORT:
-               ret = get_ext_report(snp_dev, &input);
+               /*
+                * As get_ext_report() may be called from the ioctl() path and a
+                * kernel internal path (configfs-tsm), decorate the passed
+                * buffers as user pointers.
+                */
+               io.req_data = USER_SOCKPTR((void __user *)input.req_data);
+               io.resp_data = USER_SOCKPTR((void __user *)input.resp_data);
+               ret = get_ext_report(snp_dev, &input, &io);
                break;
        default:
                break;