Re: [Part2 PATCH v6 18/38] crypto: ccp: Implement SEV_PEK_CSR ioctl command

On Thu, Oct 19, 2017 at 09:33:53PM -0500, Brijesh Singh wrote:

The SEV_PEK_CSR command can be used to generate a PEK certificate
signing request. The command is defined in SEV spec section 5.7.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <redacted>
Cc: Borislav Petkov <redacted>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Gary Hook <redacted>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-crypto@vger.kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <redacted>
---
 drivers/crypto/ccp/psp-dev.c | 69 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

Improvements-by: Borislav Petkov [off-list ref]

+static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp)
+{
+	struct sev_user_data_pek_csr input;
+	struct sev_data_pek_csr *data;
+	void *blob = NULL;
+	int ret, err;
+
+	if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
+		return -EFAULT;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* userspace wants to query CSR length */
+	if (!input.address || !input.length)
+		goto cmd;
+
+	/* 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;
+	}
+
+	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_init(NULL, &argp->error);
+	if (ret)
+		goto e_free_blob;
+
+	ret = sev_do_cmd(SEV_CMD_PEK_CSR, data, &argp->error);

This is the same issue: nothing is handling the case where sev_do_cmd()
here fails. If it doesn't matter, then you should simply do:

	sev_do_cmd(SEV_CMD_PEK_CSR, data, &argp->error);

along with explaining why we don't care about the command failing. But
simply writing into ret to overwrite it later, looks strange.

-- 
Regards/Gruss,
    Boris.

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