s390/pkey: zeroize key blobs

Key blobs for the IOCTLs PKEY_KBLOB2PROTK[23] may contain clear key
material. Zeroize the copies of these keys in kernel memory after
creating the protected key.
Reviewed-by: NHarald Freudenberger <freude@linux.ibm.com>
Signed-off-by: NHolger Dengler <dengler@linux.ibm.com>
Signed-off-by: NAlexander Gordeev <agordeev@linux.ibm.com>

drivers/s390/crypto/pkey_api.c

@@ -1293,6 +1293,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 			return PTR_ERR(kkey);
 		rc = pkey_keyblob2pkey(kkey, ktp.keylen, &ktp.protkey);
 		DEBUG_DBG("%s pkey_keyblob2pkey()=%d\n", __func__, rc);
+		memzero_explicit(kkey, ktp.keylen);
 		kfree(kkey);
 		if (rc)
 			break;
@@ -1426,6 +1427,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 					kkey, ktp.keylen, &ktp.protkey);
 		DEBUG_DBG("%s pkey_keyblob2pkey2()=%d\n", __func__, rc);
 		kfree(apqns);
+		memzero_explicit(kkey, ktp.keylen);
 		kfree(kkey);
 		if (rc)
 			break;
@@ -1552,6 +1554,7 @@ static long pkey_unlocked_ioctl(struct file *filp, unsigned int cmd,
 					protkey, &protkeylen);
 		DEBUG_DBG("%s pkey_keyblob2pkey3()=%d\n", __func__, rc);
 		kfree(apqns);
+		memzero_explicit(kkey, ktp.keylen);
 		kfree(kkey);
 		if (rc) {
 			kfree(protkey);