ftrace: Replace all non-returning strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230517145323.1522010-1-azeemshaikh38@gmail.com

kernel/trace/ftrace.c

@@ -5743,7 +5743,7 @@ bool ftrace_filter_param __initdata;
 static int __init set_ftrace_notrace(char *str)
 {
 	ftrace_filter_param = true;
-	strlcpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
+	strscpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_notrace=", set_ftrace_notrace);
@@ -5751,7 +5751,7 @@ __setup("ftrace_notrace=", set_ftrace_notrace);
 static int __init set_ftrace_filter(char *str)
 {
 	ftrace_filter_param = true;
-	strlcpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
+	strscpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_filter=", set_ftrace_filter);
@@ -5763,14 +5763,14 @@ static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
 
 static int __init set_graph_function(char *str)
 {
-	strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+	strscpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_graph_filter=", set_graph_function);
 
 static int __init set_graph_notrace_function(char *str)
 {
-	strlcpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
+	strscpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_graph_notrace=", set_graph_notrace_function);
@@ -6569,8 +6569,8 @@ static int ftrace_get_trampoline_kallsym(unsigned int symnum,
 			continue;
 		*value = op->trampoline;
 		*type = 't';
-		strlcpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN);
-		strlcpy(module_name, FTRACE_TRAMPOLINE_MOD, MODULE_NAME_LEN);
+		strscpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN);
+		strscpy(module_name, FTRACE_TRAMPOLINE_MOD, MODULE_NAME_LEN);
 		*exported = 0;
 		return 0;
 	}
@@ -6933,7 +6933,7 @@ ftrace_func_address_lookup(struct ftrace_mod_map *mod_map,
 		if (off)
 			*off = addr - found_func->ip;
 		if (sym)
-			strlcpy(sym, found_func->name, KSYM_NAME_LEN);
+			strscpy(sym, found_func->name, KSYM_NAME_LEN);
 
 		return found_func->name;
 	}
@@ -6987,8 +6987,8 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
 
 			*value = mod_func->ip;
 			*type = 'T';
-			strlcpy(name, mod_func->name, KSYM_NAME_LEN);
-			strlcpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);
+			strscpy(name, mod_func->name, KSYM_NAME_LEN);
+			strscpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);
 			*exported = 1;
 			preempt_enable();
 			return 0;