[PATCH v1 1/1] s390/zcrypt: Fix uninitialized padding in CRT key structure

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

The zcrypt_type6_crt_key() function leaves padding bytes uninitialized
between key components and the modulus in the CCA CRT key token. These
padding bytes are sent to the crypto card, potentially leaking kernel
memory contents.

The initial memset() only zeros fixed structure fields, not the
flexible array member key_parts[] where the padding resides. While key
components are properly copied from userspace, the calculated pad_len
bytes between them remain uninitialized.

Fix by explicitly zeroing the padding bytes after copying the CRT key
components.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
---
 drivers/s390/crypto/zcrypt_cca_key.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/s390/crypto/zcrypt_cca_key.h b/drivers/s390/crypto/zcrypt_cca_key.h
index f5907b67db29..8a69eed75040 100644
--- a/drivers/s390/crypto/zcrypt_cca_key.h
+++ b/drivers/s390/crypto/zcrypt_cca_key.h
@@ -219,6 +219,7 @@ static inline int zcrypt_type6_crt_key(struct ica_rsa_modexpo_crt *crt, void *p)
 	    copy_from_user(key->key_parts + 2 * long_len + 2 * short_len,
 			   crt->u_mult_inv, long_len))
 		return -EFAULT;
+	memset(key->key_parts + 3 * long_len + 2 * short_len, 0, pad_len);
 	memset(key->key_parts + 3 * long_len + 2 * short_len + pad_len,
 	       0xff, crt->inputdatalength);
 	pub = (struct cca_public_sec *)(key->key_parts + key_len);
-- 
2.43.0