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

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Date:   Mon, 31 May 2021 19:11:16 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        syzbot+08a7d8b51ea048a74ffb@...kaller.appspotmail.com
Subject: Re: [PATCH] ALSA: control led: fix memory leak in snd_ctl_led_register

On Mon, May 31, 2021 at 7:07 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> 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.  :)

Sure. No problem. I will send a v2 patch after reading the whole thread again.

>
> 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);
> }
>