kernel: ksud, sucompat: micro-opt, drop redundant memset before strncpy

its not like were doing
memset(dest, 0, sizeof(dest));
strncat(dest, var, bytes);
for that copy.

that memset seems unneeded
we also use strncpy itself to do proper error and oob check
and we null term when successful

Signed-off-by: backslashxx <[email protected]>

Author: backslashxx

kernel/ksud.c

@@ -495,8 +495,11 @@ __maybe_unused static int __ksu_handle_execve_ksud(const char __user *filename_u
 	if (!filename_user)
 		return 0;
 
-	memset(path, 0, sizeof(path));
-	ksu_strncpy_from_user_nofault(path, filename_user, 32);
+	long len = ksu_strncpy_from_user_nofault(path, filename_user, 32);
+	if (len <= 0 || len > 32)
+		return 0;
+
+	path[sizeof(path) - 1] = '\0';
 
 	return __ksu_handle_execveat_ksud(AT_FDCWD, path, argv, NULL, NULL);
 }

kernel/sucompat.c

@@ -64,8 +64,11 @@ int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
 	}
 
 	char path[sizeof(su) + 1];
-	memset(path, 0, sizeof(path));
-	ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));
+	long len = ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));
+	if (len <= 0 || len > sizeof(path))
+		return 0;
+
+	path[sizeof(path) - 1] = '\0';
 
 	if (unlikely(!memcmp(path, su, sizeof(su)))) {
 		pr_info("faccessat su->sh!\n");
@@ -93,8 +96,11 @@ int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags)
 	}
 
 	char path[sizeof(su) + 1];
-	memset(path, 0, sizeof(path));
-	ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));
+	long len = ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));
+	if (len <= 0 || len > sizeof(path))
+		return 0;
+
+	path[sizeof(path) - 1] = '\0';
 
 	if (unlikely(!memcmp(path, su, sizeof(su)))) {
 		pr_info("newfstatat su->sh!\n");