rethook: fix a potential memleak in rethook_alloc()

In rethook_alloc(), the variable rh is not freed or passed out
if handler is NULL, which could lead to a memleak, fix it.

Link: https://lore.kernel.org/all/[email protected]/
[Masami: Add "rethook:" tag to the title.]

Fixes: 54ecbe6 ("rethook: Add a generic return hook")
Cc: [email protected]
Signed-off-by: Yi Yang <[email protected]>
Acke-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

Author: Yi Yang

kernel/trace/rethook.c

@@ -83,8 +83,10 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler)
 {
 	struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
 
-	if (!rh || !handler)
+	if (!rh || !handler) {
+		kfree(rh);
 		return NULL;
+	}
 
 	rh->data = data;
 	rh->handler = handler;