From 13dc15a3f5fd7f884e4bfa8c011a0ae868df12ae Mon Sep 17 00:00:00 2001
From: John Allen <john.allen@amd.com>
Date: Wed, 18 May 2022 15:31:26 +0000
Subject: [PATCH] crypto: ccp - Use kzalloc for sev ioctl interfaces to prevent kernel memory leak
Git-commit: 13dc15a3f5fd7f884e4bfa8c011a0ae868df12ae
Patch-mainline: v6.0-rc1
References: git-fixes

For some sev ioctl interfaces, input may be passed that is less than or
equal to SEV_FW_BLOB_MAX_SIZE, but larger than the data that PSP
firmware returns. In this case, kmalloc will allocate memory that is the
size of the input rather than the size of the data. Since PSP firmware
doesn't fully overwrite the buffer, the sev ioctl interfaces with the
issue may return uninitialized slab memory.

Currently, all of the ioctl interfaces in the ccp driver are safe, but
to prevent future problems, change all ioctl interfaces that allocate
memory with kmalloc to use kzalloc and memset the data buffer to zero
in sev_ioctl_do_platform_status.

Fixes: 38103671aad3 ("crypto: ccp: Use the stack and common buffer for status commands")
Fixes: e799035609e15 ("crypto: ccp: Implement SEV_PEK_CSR ioctl command")
Fixes: 76a2b524a4b1d ("crypto: ccp: Implement SEV_PDH_CERT_EXPORT ioctl command")
Fixes: d6112ea0cb344 ("crypto: ccp - introduce SEV_GET_ID2 command")
Cc: stable@vger.kernel.org
Reported-by: Andy Nguyen <theflow@google.com>
Suggested-by: David Rientjes <rientjes@google.com>
Suggested-by: Peter Gonda <pgonda@google.com>
Signed-off-by: John Allen <john.allen@amd.com>
Reviewed-by: Peter Gonda <pgonda@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/crypto/ccp/sev-dev.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 799b476fc3e8..0c92d940ac4e 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -577,6 +577,8 @@ static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp)
 	struct sev_user_data_status data;
 	int ret;
 
+	memset(&data, 0, sizeof(data));
+
 	ret = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, &data, &argp->error);
 	if (ret)
 		return ret;
@@ -630,7 +632,7 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp, bool writable)
 	if (input.length > SEV_FW_BLOB_MAX_SIZE)
 		return -EFAULT;
 
-	blob = kmalloc(input.length, GFP_KERNEL);
+	blob = kzalloc(input.length, GFP_KERNEL);
 	if (!blob)
 		return -ENOMEM;
 
@@ -854,7 +856,7 @@ static int sev_ioctl_do_get_id2(struct sev_issue_cmd *argp)
 	input_address = (void __user *)input.address;
 
 	if (input.address && input.length) {
-		id_blob = kmalloc(input.length, GFP_KERNEL);
+		id_blob = kzalloc(input.length, GFP_KERNEL);
 		if (!id_blob)
 			return -ENOMEM;
 
@@ -973,14 +975,14 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
 	if (input.cert_chain_len > SEV_FW_BLOB_MAX_SIZE)
 		return -EFAULT;
 
-	pdh_blob = kmalloc(input.pdh_cert_len, GFP_KERNEL);
+	pdh_blob = kzalloc(input.pdh_cert_len, GFP_KERNEL);
 	if (!pdh_blob)
 		return -ENOMEM;
 
 	data.pdh_cert_address = __psp_pa(pdh_blob);
 	data.pdh_cert_len = input.pdh_cert_len;
 
-	cert_blob = kmalloc(input.cert_chain_len, GFP_KERNEL);
+	cert_blob = kzalloc(input.cert_chain_len, GFP_KERNEL);
 	if (!cert_blob) {
 		ret = -ENOMEM;
 		goto e_free_pdh;
-- 
2.35.3