ftrace: Fix memleak when unregistering dynamic ops when tracing disabled

If function tracing is disabled by the user via the function-trace option or
the proc sysctl file, and a ftrace_ops that was allocated on the heap is
unregistered, then the shutdown code exits out without doing the proper
clean up. This was found via kmemleak and running the ftrace selftests, as
one of the tests unregisters with function tracing disabled.

 # cat kmemleak
unreferenced object 0xffffffffa0020000 (size 4096):
  comm "swapper/0", pid 1, jiffies 4294668889 (age 569.209s)
  hex dump (first 32 bytes):
    55 ff 74 24 10 55 48 89 e5 ff 74 24 18 55 48 89  U.t$.UH...t$.UH.
    e5 48 81 ec a8 00 00 00 48 89 44 24 50 48 89 4c  .H......H.D$PH.L
  backtrace:
    [<ffffffff81d64665>] kmemleak_vmalloc+0x85/0xf0
    [<ffffffff81355631>] __vmalloc_node_range+0x281/0x3e0
    [<ffffffff8109697f>] module_alloc+0x4f/0x90
    [<ffffffff81091170>] arch_ftrace_update_trampoline+0x160/0x420
    [<ffffffff81249947>] ftrace_startup+0xe7/0x300
    [<ffffffff81249bd2>] register_ftrace_function+0x72/0x90
    [<ffffffff81263786>] trace_selftest_ops+0x204/0x397
    [<ffffffff82bb8971>] trace_selftest_startup_function+0x394/0x624
    [<ffffffff81263a75>] run_tracer_selftest+0x15c/0x1d7
    [<ffffffff82bb83f1>] init_trace_selftests+0x75/0x192
    [<ffffffff81002230>] do_one_initcall+0x90/0x1e2
    [<ffffffff82b7d620>] kernel_init_freeable+0x350/0x3fe
    [<ffffffff81d61ec3>] kernel_init+0x13/0x122
    [<ffffffff81d72c6a>] ret_from_fork+0x2a/0x40
    [<ffffffffffffffff>] 0xffffffffffffffff

Cc: stable@vger.kernel.org
Fixes: 12cce594fa ("ftrace/x86: Allow !CONFIG_PREEMPT dynamic ops to use allocated trampolines")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -2828,13 +2828,14 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command)
 
 	if (!command || !ftrace_enabled) {
 		/*
-		 * If these are per_cpu ops, they still need their
-		 * per_cpu field freed. Since, function tracing is
+		 * If these are dynamic or per_cpu ops, they still
+		 * need their data freed. Since, function tracing is
 		 * not currently active, we can just free them
 		 * without synchronizing all CPUs.
 		 */
-		if (ops->flags & FTRACE_OPS_FL_PER_CPU)
-			per_cpu_ops_free(ops);
+		if (ops->flags & (FTRACE_OPS_FL_DYNAMIC | FTRACE_OPS_FL_PER_CPU))
+			goto free_ops;
+
 		return 0;
 	}
 
@@ -2900,6 +2901,7 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command)
 		if (IS_ENABLED(CONFIG_PREEMPT))
 			synchronize_rcu_tasks();
 
+ free_ops:
 		arch_ftrace_trampoline_free(ops);
 
 		if (ops->flags & FTRACE_OPS_FL_PER_CPU)