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SubjectRe: [Part2 PATCH v5.1 12.7/31] crypto: ccp: Implement SEV_PEK_CSR ioctl command
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On 10/12/17 9:24 PM, Brijesh Singh wrote:
>
> On 10/12/17 2:53 PM, Borislav Petkov wrote:
> ...
>
>> Ok, a couple of things here:
>>
>> * Move the checks first and the allocations second so that you allocate
>> memory only after all checks have been passed and you don't allocate
>> pointlessly.
>
> I assume you mean performing the SEV state check before allocating the
> memory for the CSR blob, right ? In my patches, I typically perform all
> the SW specific checks and allocation before invoking the HW routines.
> Handling the PSP commands will take longer compare to kmalloc() or
> access_ok() etc. If its not a big deal then I would prefer to keep that
> way.
>
>
>> * That:
>>
>> if (state == SEV_STATE_WORKING) {
>> ret = -EBUSY;
>> goto e_free_blob;
>> } else if (state == SEV_STATE_UNINIT) {
>> ret = sev_firmware_init(&argp->error);
>> if (ret)
>> goto e_free_blob;
>> do_shutdown = 1;
>> }
>>
>> is a repeating pattern. Perhaps it should be called
>> sev_firmware_reinit() and called by other functions.
>
>> * The rest is simplifications and streamlining.
>>
>> ---
>> diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
>> index e3ee68afd068..d41f5448a25b 100644
>> --- a/drivers/crypto/ccp/psp-dev.c
>> +++ b/drivers/crypto/ccp/psp-dev.c
>> @@ -302,33 +302,30 @@ static int sev_ioctl_pek_csr(struct sev_issue_cmd *argp)
>> 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;
>> +
>> + if (!input.address)
>> + return -EINVAL;
>> +


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. 


>> + /* 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)
>> 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;
>> - }
>> -
>> - blob = kmalloc(input.length, GFP_KERNEL);
>> - if (!blob) {
>> - ret = -ENOMEM;
>> - 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;
>> +
>> ret = sev_platform_get_state(&state, &argp->error);
>> if (ret)
>> goto e_free_blob;
>> @@ -349,25 +346,23 @@ 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);
>>
>> input.length = data->len;
>>
>> /* copy blob to userspace */
>> - if (blob &&
>> - copy_to_user((void __user *)(uintptr_t)input.address,
>> - blob, input.length)) {
>> + 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);
>> + ret = sev_do_cmd(SEV_CMD_SHUTDOWN, 0, NULL);
>> +
>> e_free_blob:
>> kfree(blob);
>> e_free:
>> @@ -408,10 +403,10 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
>> ret = sev_ioctl_pdh_gen(&input);
>> break;
>>
>> - case SEV_PEK_CSR: {
>> + case SEV_PEK_CSR:
>> ret = sev_ioctl_pek_csr(&input);
>> break;
>> - }
>> +
>> default:
>> ret = -EINVAL;
>> goto out;
>>

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