[PATCH 3/5] smb: client: Clear sensitive stack data in cifsencrypt.c

[Thomas Huth]

From: Thomas Huth <thuth@xxxxxxxxxx>

Make sure to not leak hash data via the stack, clear it
with memzero_explicit() before leaving the function.

Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
 fs/smb/client/cifsencrypt.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c
index 34804e9842a80..71a2a59123f57 100644
--- a/fs/smb/client/cifsencrypt.c
+++ b/fs/smb/client/cifsencrypt.c
@@ -249,12 +249,13 @@ static int calc_ntlmv2_hash(struct cifs_ses *ses, char *ntlmv2_hash,
 	E_md4hash(ses->password, nt_hash, nls_cp);
 
 	hmac_md5_init_usingrawkey(&hmac_ctx, nt_hash, CIFS_NTHASH_SIZE);
+	memzero_explicit(nt_hash, sizeof(nt_hash));
 
 	/* convert ses->user_name to unicode */
 	len = ses->user_name ? strlen(ses->user_name) : 0;
 	user = kmalloc(2 + (len * 2), GFP_KERNEL);
 	if (user == NULL)
-		return -ENOMEM;
+		goto out_nomem;
 
 	if (len) {
 		len = cifs_strtoUTF16(user, ses->user_name, len, nls_cp);
@@ -272,7 +273,7 @@ static int calc_ntlmv2_hash(struct cifs_ses *ses, char *ntlmv2_hash,
 
 		domain = kmalloc(2 + (len * 2), GFP_KERNEL);
 		if (domain == NULL)
-			return -ENOMEM;
+			goto out_nomem;
 
 		len = cifs_strtoUTF16((__le16 *)domain, ses->domainName, len,
 				      nls_cp);
@@ -284,7 +285,7 @@ static int calc_ntlmv2_hash(struct cifs_ses *ses, char *ntlmv2_hash,
 
 		server = kmalloc(2 + (len * 2), GFP_KERNEL);
 		if (server == NULL)
-			return -ENOMEM;
+			goto out_nomem;
 
 		len = cifs_strtoUTF16((__le16 *)server, ses->ip_addr, len, nls_cp);
 		hmac_md5_update(&hmac_ctx, (const u8 *)server, 2 * len);
@@ -293,6 +294,10 @@ static int calc_ntlmv2_hash(struct cifs_ses *ses, char *ntlmv2_hash,
 
 	hmac_md5_final(&hmac_ctx, ntlmv2_hash);
 	return 0;
+
+out_nomem:
+	memzero_explicit(&hmac_ctx, sizeof(hmac_ctx));
+	return -ENOMEM;
 }
 
 static void CalcNTLMv2_response(const struct cifs_ses *ses, char *ntlmv2_hash)
@@ -463,6 +468,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
 	rc = 0;
 unlock:
 	cifs_server_unlock(ses->server);
+	memzero_explicit(ntlmv2_hash, sizeof(ntlmv2_hash));
 setup_ntlmv2_rsp_ret:
 	kfree_sensitive(tiblob);
 
-- 
2.55.0