From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>, Shuah Khan <shuah@kernel.org>,
Tom Zanussi <tom.zanussi@linux.intel.com>,
Hiraku Toyooka <hiraku.toyooka@cybertrust.co.jp>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 1/3] [BUGFIX] tracing: Fix double free of event_trigger_data
Date: Tue, 24 Jul 2018 16:49:59 -0400 [thread overview]
Message-ID: <20180724164959.3cbc1422@gandalf.local.home> (raw)
In-Reply-To: <20180725000909.6c8b2f3881ee75c4f6bd466b@kernel.org>
On Wed, 25 Jul 2018 00:09:09 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> Hmm, your patch seems to leak a memory since event_trigger_init() will
> be called twice on same trigger_data (Note that event_trigger_init()
> does not init ref counter, but increment it.) So we should decrement
> it when we find it is succeeded. Moreover, if register_trigger()
Good catch, and easily fixed.
> fails before calling data->ops->init() (see -EEXIST case), the ref
> counter will be 0 (-1 +1). But if it fails after data->ops->init(),
> the ref counter will be 1 (-1 +1 +1). It still be unstable.
> (Ah, that means we may have another trouble...)
I'm not sure there's a problem here. I now have:
out_reg:
/* Up the trigger_data count to make sure reg doesn't free it on failuer */
event_trigger_init(trigger_ops, trigger_data);
ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
/*
* The above returns on success the # of functions enabled,
* but if it didn't find any functions it returns zero.
* Consider no functions a failure too.
*/
if (!ret) {
ret = -ENOENT;
} else if (ret > 0)
ret = 0;
/* Down the counter of trigger_data or free it if not used anymore */
event_trigger_free(trigger_ops, trigger_data);
out:
return ret;
Thus we increment trigger_data before calling reg, and free it
afterward. But if reg() did an init too, then the event_trigger_free()
just decs the ref counter.
As for register_trigger()
>
> >
> > P.S. This brings up another minor bug. The failure should return ENOMEM
> > not ENOENT.
>
> Hmm it seems we should review the register_trigger() implementation.
> It should return the return value of trace_event_trigger_enable_disable(),
> shouldn't it?
>
Yeah, that's not done well. I'll fix it up.
Thanks for pointing it out.
-- Steve
next prev parent reply other threads:[~2018-07-24 20:50 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-13 16:27 [PATCH 0/3] tracing: Fix bugs on snapshot feature Masami Hiramatsu
2018-07-13 16:27 ` [PATCH 1/3] [BUGFIX] tracing: Fix double free of event_trigger_data Masami Hiramatsu
2018-07-24 2:10 ` Steven Rostedt
2018-07-24 15:09 ` Masami Hiramatsu
2018-07-24 20:49 ` Steven Rostedt [this message]
2018-07-24 21:30 ` Steven Rostedt
2018-07-24 23:13 ` Steven Rostedt
2018-07-25 1:16 ` Masami Hiramatsu
2018-07-25 2:41 ` Steven Rostedt
2018-07-25 14:14 ` Masami Hiramatsu
2018-07-25 16:01 ` Tom Zanussi
2018-07-25 16:09 ` Steven Rostedt
2018-07-25 1:05 ` Masami Hiramatsu
2018-07-13 16:28 ` [PATCH 2/3] [BUGFIX] ring_buffer: tracing: Inherit the tracing setting to next ring buffer Masami Hiramatsu
2018-07-24 2:25 ` Steven Rostedt
2018-07-24 14:30 ` Masami Hiramatsu
2018-07-13 16:28 ` [PATCH 3/3] selftests/ftrace: Add snapshot and tracing_on test case Masami Hiramatsu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180724164959.3cbc1422@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=hiraku.toyooka@cybertrust.co.jp \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=shuah@kernel.org \
--cc=stable@vger.kernel.org \
--cc=tom.zanussi@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).