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SubjectRe: [Part2 PATCH v5.1 12.7/31] crypto: ccp: Implement SEV_PEK_CSR ioctl command
On Thu, Oct 12, 2017 at 11:13:44PM -0500, Brijesh Singh wrote:
> As per the spec, its perfectly legal to pass input.address = 0x0 and
> input.length = 0x0. If userspace wants to query CSR length then it will
> fill all the fields with. In response, FW will return error
> (LENGTH_TO_SMALL) and input.length will be filled with the expected
> length. Several command work very similar (e.g PEK_CSR,
> PEK_CERT_EXPORT). A typical usage from userspace will be:
>
> - query the length of the blob (call command with all fields set to zero)
> - SEV FW will response with expected length
> - userspace allocate the blob and retries the command. 

Ok, let's make that a clearer and more precise by explicitly checking
the query case:

+ /* Userspace wants to query CSR length */
+ if (!input.address && !input.length)
+ goto cmd;

and commenting why we're doing this.

The rest is cleanups.

---
diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index e3ee68afd068..e10f507f9a60 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -299,36 +299,37 @@ static int sev_ioctl_pek_csr(struct sev_issue_cmd *argp)
struct sev_user_data_pek_csr input;
struct sev_data_pek_csr *data;
int do_shutdown = 0;
+ void *blob = NULL;
int ret, state;
- void *blob;

- if (copy_from_user(&input, (void __user *)(uintptr_t)argp->data,
- sizeof(struct sev_user_data_pek_csr)))
+ if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
return -EFAULT;

data = kzalloc(sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;

- /* allocate a temporary physical contigous buffer to store the CSR blob */
- blob = NULL;
- if (input.address) {
- if (!access_ok(VERIFY_WRITE, input.address, input.length) ||
- input.length > SEV_FW_BLOB_MAX_SIZE) {
- ret = -EFAULT;
- goto e_free;
- }
+ /* Userspace wants to query CSR length */
+ if (!input.address && !input.length)
+ goto cmd;

- blob = kmalloc(input.length, GFP_KERNEL);
- if (!blob) {
- ret = -ENOMEM;
- goto e_free;
- }
+ /* allocate a physically contiguous buffer to store the CSR blob */
+ if (!access_ok(VERIFY_WRITE, input.address, input.length) ||
+ input.length > SEV_FW_BLOB_MAX_SIZE) {
+ ret = -EFAULT;
+ goto e_free;
+ }

- data->address = __psp_pa(blob);
- data->len = input.length;
+ blob = kmalloc(input.length, GFP_KERNEL);
+ if (!blob) {
+ ret = -ENOMEM;
+ goto e_free;
}

+ data->address = __psp_pa(blob);
+ data->len = input.length;
+
+cmd:
ret = sev_platform_get_state(&state, &argp->error);
if (ret)
goto e_free_blob;
@@ -349,25 +350,26 @@ static int sev_ioctl_pek_csr(struct sev_issue_cmd *argp)
do_shutdown = 1;
}

- ret = sev_handle_cmd(SEV_CMD_PEK_CSR, data, &argp->error);
+ ret = sev_do_cmd(SEV_CMD_PEK_CSR, data, &argp->error);

+ /*
+ * If we query the CSR length, FW responded with the expected length.
+ */
input.length = data->len;

- /* copy blob to userspace */
- if (blob &&
- copy_to_user((void __user *)(uintptr_t)input.address,
- blob, input.length)) {
- ret = -EFAULT;
- goto e_shutdown;
+ if (blob) {
+ if (copy_to_user((void __user *)input.address, blob, input.length)) {
+ ret = -EFAULT;
+ goto e_shutdown;
+ }
}

- if (copy_to_user((void __user *)(uintptr_t)argp->data, &input,
- sizeof(struct sev_user_data_pek_csr)))
+ if (copy_to_user((void __user *)argp->data, &input, sizeof(input)))
ret = -EFAULT;

e_shutdown:
if (do_shutdown)
- sev_handle_cmd(SEV_CMD_SHUTDOWN, 0, NULL);
+ sev_do_cmd(SEV_CMD_SHUTDOWN, 0, NULL);
e_free_blob:
kfree(blob);
e_free:
--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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