thunderbolt: Compare HMAC values in constant time

To prevent timing attacks, HMAC value comparison needs to be constant
time. Replace the memcmp() with the correct function, crypto_memneq().

Fixes: f67cf491175a ("thunderbolt: Add support for Internal Connection Manager (ICM)")
Signed-off-by: Eric Biggers <[e-mail]>
Signed-off-by: Mika Westerberg <[e-mail]>

drivers/thunderbolt/domain.c

···
 #include <linux/slab.h>
 #include <linux/random.h>
 #include <crypto/hash.h>
+#include <crypto/utils.h>
 
 #include "tb.h"
 
···
 		goto err_free_shash;
 
 	/* The returned HMAC must match the one we calculated */
-	if (memcmp(response, hmac, sizeof(hmac))) {
+	if (crypto_memneq(response, hmac, sizeof(hmac))) {
 		ret = -EKEYREJECTED;
 		goto err_free_shash;
 	}