[PATCH 2/2] scsi: target: use constant-time crypto_memneq for CHAP digests

[David Disseldorp <ddiss@suse.de>]

A constant-time memory comparison is more suitable than plain memcmp()
for authentication digest comparison.
CHAP digests use an authenticator-provided random challenge, so any
timing side-channel shouldn't be easily exploitable.

Reported-by: Sashiko (gemini/gemini-3.1-pro-preview)
Link: https://sashiko.dev/#/patchset/20260521151121.808477-1-hossu.alexandru%40gmail.com
Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 drivers/target/iscsi/iscsi_target_auth.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
index 5858cc3089796..f3c0cdd318300 100644
--- a/drivers/target/iscsi/iscsi_target_auth.c
+++ b/drivers/target/iscsi/iscsi_target_auth.c
@@ -9,6 +9,7 @@
  ******************************************************************************/
 
 #include <crypto/hash.h>
+#include <crypto/utils.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/err.h>
@@ -408,7 +409,7 @@ static int chap_server_compute_hash(
 	pr_debug("[server] %s Server Digest: %s\n",
 		chap->digest_name, response);
 
-	if (memcmp(server_digest, client_digest, chap->digest_size) != 0) {
+	if (crypto_memneq(server_digest, client_digest, chap->digest_size)) {
 		pr_debug("[server] %s Digests do not match!\n\n",
 			chap->digest_name);
 		goto out;
-- 
2.51.0