linux-kernel - Re: [PATCH] ALSA: control led: fix memory leak in snd_ctl_led

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Date:   Mon, 31 May 2021 14:07:42 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>
Cc:     perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
Subject: Re: [PATCH] ALSA: control led: fix memory leak in
 snd_ctl_led_register

I've also created a Smatch check for missing ->release() functions.  It
find one bug in that file.  There are other bugs, but the static checker
is not clever enough to find them.  I expect Smatch will get smarter
about this in the coming year.

sound/core/control_led.c:685 snd_ctl_led_sysfs_add() warn: calling put_device() with no ->release() function

So, yeay, I feel like this thread has been useful and I now understand
put_device() a little better.  Please review the email thread again and
send a v2 patch.  :)

regards,
dan carpenter

/*
 * Copyright (C) 2021 Oracle.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
 */

#include "smatch.h"
#include "smatch_extra.h"

static int my_id;

static void match_put_device(struct expression *expr, const char *name, struct symbol *sym, void *data)
{
	struct smatch_state *state;

	state = get_state(SMATCH_EXTRA, name, sym);
	if (!state ||
	    estate_min(state).value != 0 ||
	    estate_max(state).value != 0)
		return;

	sm_warning("calling put_device() with no ->release() function");
}

void check_no_release(int id)
{
	my_id = id;

	if (option_project != PROJ_KERNEL)
		return;

	add_function_param_key_hook("put_device", &match_put_device, 0, "$->release", NULL);
	add_function_param_key_hook("device_unregister", &match_put_device, 0, "$->release", NULL);
}