linux-kernel - Re: [PATCH] tracing: Fix double free of event_trigger

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Message-ID: <20180725155321.3e677387@gandalf.local.home>
Date:   Wed, 25 Jul 2018 15:53:21 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Hiraku Toyooka <hiraku.toyooka@...ertrust.co.jp>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] tracing: Fix double free of event_trigger_data

On Wed, 25 Jul 2018 15:29:04 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> Nope, this doesn't work. It's a little more complex than the other one.
> I'll just leave it, and fix the reg code for 4.19.

I take this back. Looks like it just needs to be handled slightly
differently. Thoughts?

-- Steve

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d18ec0e58be2..5dea177cef53 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1420,6 +1420,9 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
 		goto out;
 	}
 
+	/* Up the trigger_data count to make sure nothing frees it on failure */
+	event_trigger_init(trigger_ops, trigger_data);
+
 	if (trigger) {
 		number = strsep(&trigger, ":");
 
@@ -1470,6 +1473,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
 		goto out_disable;
 	/* Just return zero, not the number of enabled functions */
 	ret = 0;
+	event_trigger_free(trigger_ops, trigger_data);
  out:
 	return ret;
 
@@ -1480,7 +1484,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
  out_free:
 	if (cmd_ops->set_filter)
 		cmd_ops->set_filter(NULL, trigger_data, NULL);
-	kfree(trigger_data);
+	event_trigger_free(trigger_ops, trigger_data);
 	kfree(enable_data);
 	goto out;
 }