[PATCH v1 1/1] s390/zcrypt: Fix missing mem scrub at clear key import in cca_clr2cipherkey()

[Harald Freudenberger <freude@linux.ibm.com>]

The helper function _ip_cprb_helper() uses internal buffer memory for
building and processing CPRBs. After use this buffer was never
scrubbed which could lead to leaving for example clear key material in
memory which could be exposed via tricky reuse of this same memory.

Extent the _ip_cprb_helper() function with another parameter 'scrub'
used to steer scrubbing of this buffer. So now the caller has the
opportunity to decide if scrubbing is needed or not.

Extent the clear key to secure key token import process in function
cca_clr2cipherkey() to tell the helper function from above to scrub
the cprb buffer when the clear key value is part of the request data.

Overall this cleans the internal used buffer in case of clear key
import to prevent sensitive data to get exposed.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Cc: stable@vger.kernel.org
---
 drivers/s390/crypto/zcrypt_ccamisc.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/crypto/zcrypt_ccamisc.c b/drivers/s390/crypto/zcrypt_ccamisc.c
index 84936a795b95..6a237e880b40 100644
--- a/drivers/s390/crypto/zcrypt_ccamisc.c
+++ b/drivers/s390/crypto/zcrypt_ccamisc.c
@@ -971,7 +971,8 @@ static int _ip_cprb_helper(u16 cardnr, u16 domain,
 			   int clr_key_bit_size,
 			   u8 *key_token,
 			   int *key_token_size,
-			   u32 xflags)
+			   u32 xflags,
+			   bool scrub)
 {
 	int rc, n;
 	u8 *mem, *ptr;
@@ -1111,7 +1112,7 @@ static int _ip_cprb_helper(u16 cardnr, u16 domain,
 	*key_token_size = t->len;
 
 out:
-	free_cprbmem(mem, PARMBSIZE, false, xflags);
+	free_cprbmem(mem, PARMBSIZE, scrub, xflags);
 	return rc;
 }
 
@@ -1162,28 +1163,32 @@ int cca_clr2cipherkey(u16 card, u16 dom, u32 keybitsize, u32 keygenflags,
 	 * 4/4 COMPLETE the secure cipher key import
 	 */
 	rc = _ip_cprb_helper(card, dom, "AES     ", "FIRST   ", "MIN3PART",
-			     exorbuf, keybitsize, token, &tokensize, xflags);
+			     exorbuf, keybitsize, token, &tokensize,
+			     xflags, false);
 	if (rc) {
 		ZCRYPT_DBF_ERR("%s clear key import 1/4 with CSNBKPI2 failed, rc=%d\n",
 			       __func__, rc);
 		goto out;
 	}
 	rc = _ip_cprb_helper(card, dom, "AES     ", "ADD-PART", NULL,
-			     clrkey, keybitsize, token, &tokensize, xflags);
+			     clrkey, keybitsize, token, &tokensize,
+			     xflags, true);
 	if (rc) {
 		ZCRYPT_DBF_ERR("%s clear key import 2/4 with CSNBKPI2 failed, rc=%d\n",
 			       __func__, rc);
 		goto out;
 	}
 	rc = _ip_cprb_helper(card, dom, "AES     ", "ADD-PART", NULL,
-			     exorbuf, keybitsize, token, &tokensize, xflags);
+			     exorbuf, keybitsize, token, &tokensize,
+			     xflags, false);
 	if (rc) {
 		ZCRYPT_DBF_ERR("%s clear key import 3/4 with CSNBKPI2 failed, rc=%d\n",
 			       __func__, rc);
 		goto out;
 	}
 	rc = _ip_cprb_helper(card, dom, "AES     ", "COMPLETE", NULL,
-			     NULL, keybitsize, token, &tokensize, xflags);
+			     NULL, keybitsize, token, &tokensize,
+			     xflags, false);
 	if (rc) {
 		ZCRYPT_DBF_ERR("%s clear key import 4/4 with CSNBKPI2 failed, rc=%d\n",
 			       __func__, rc);
-- 
2.43.0