From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: kbuild@lists.01.org, Drew Fustini <drew@beagleboard.org>,
Linus Walleij <linus.walleij@linaro.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tony Lindgren <tony@atomide.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
Jason Kridner <jkridner@beagleboard.org>,
Robert Nelson <robertcnelson@beagleboard.org>,
kbuild test robot <lkp@intel.com>,
kbuild-all@lists.01.org
Subject: Re: [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file
Date: Wed, 10 Feb 2021 19:39:16 +0100 [thread overview]
Message-ID: <CAMuHMdUTG-0PMsP--i4KE2RA_zOaQgpUDksvtU8dLPW9dSpoug@mail.gmail.com> (raw)
In-Reply-To: <20210210182044.GY2696@kadam>
Hi Dan,
On Wed, Feb 10, 2021 at 7:21 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 694 buf = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME * 2, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 695 if (!buf)
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 696 return -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 697
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 698 fname = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 699 if (!fname) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 700 ret = -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 701 goto free_buf;
>
> The gotos are out of order. They should be in mirror/reverse order of
> the allocations:
>
> free_gmane:
> devm_kfree(pctldev->dev, gname);
> free_fname:
> devm_kfree(pctldev->dev, fname);
> free_buf:
> devm_kfree(pctldev->dev, buf);
>
> But also why do we need to use devm_kfree() at all? I thought the whole
> point of devm_ functions was that they are garbage collected
> automatically for you. Can we not just delete all error handling and
> return -ENOMEM here?
No, because the lifetime of the objects allocated here does not match the
lifetime of dev. If they're not freed here, they will only be freed when the
device is unbound. As the user can access the sysfs files at will, he can
OOM the system.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
WARNING: multiple messages have this Message-ID (diff)
From: Geert Uytterhoeven <geert@linux-m68k.org>
To: kbuild-all@lists.01.org
Subject: Re: [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file
Date: Wed, 10 Feb 2021 19:39:16 +0100 [thread overview]
Message-ID: <CAMuHMdUTG-0PMsP--i4KE2RA_zOaQgpUDksvtU8dLPW9dSpoug@mail.gmail.com> (raw)
In-Reply-To: <20210210182044.GY2696@kadam>
[-- Attachment #1: Type: text/plain, Size: 1840 bytes --]
Hi Dan,
On Wed, Feb 10, 2021 at 7:21 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 694 buf = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME * 2, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 695 if (!buf)
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 696 return -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 697
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 698 fname = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME, GFP_KERNEL);
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 699 if (!fname) {
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 700 ret = -ENOMEM;
> 99b2f99aa41aa7 Drew Fustini 2021-02-09 701 goto free_buf;
>
> The gotos are out of order. They should be in mirror/reverse order of
> the allocations:
>
> free_gmane:
> devm_kfree(pctldev->dev, gname);
> free_fname:
> devm_kfree(pctldev->dev, fname);
> free_buf:
> devm_kfree(pctldev->dev, buf);
>
> But also why do we need to use devm_kfree() at all? I thought the whole
> point of devm_ functions was that they are garbage collected
> automatically for you. Can we not just delete all error handling and
> return -ENOMEM here?
No, because the lifetime of the objects allocated here does not match the
lifetime of dev. If they're not freed here, they will only be freed when the
device is unbound. As the user can access the sysfs files at will, he can
OOM the system.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert(a)linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2021-02-10 18:43 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 7:49 [PATCH v2 0/2] pinctrl: pinmux: Add pinmux-select debugfs file Drew Fustini
2021-02-10 7:49 ` [PATCH v2 1/2] pinctrl: use to octal permissions for debugfs files Drew Fustini
2021-02-10 8:30 ` Joe Perches
2021-02-10 10:18 ` Andy Shevchenko
2021-02-10 12:36 ` Joe Perches
2021-02-10 21:21 ` Drew Fustini
2021-02-10 23:12 ` Joe Perches
2021-02-10 8:31 ` Geert Uytterhoeven
2021-02-10 10:14 ` Andy Shevchenko
2021-02-10 10:16 ` Andy Shevchenko
2021-02-10 7:49 ` [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file Drew Fustini
2021-02-10 8:35 ` Geert Uytterhoeven
2021-02-10 9:56 ` Andy Shevchenko
2021-02-10 17:31 ` Drew Fustini
2021-02-10 18:20 ` Dan Carpenter
2021-02-10 18:20 ` Dan Carpenter
2021-02-10 18:20 ` Dan Carpenter
2021-02-10 18:39 ` Geert Uytterhoeven [this message]
2021-02-10 18:39 ` Geert Uytterhoeven
2021-02-10 19:05 ` Dan Carpenter
2021-02-10 19:05 ` Dan Carpenter
2021-02-10 19:05 ` Dan Carpenter
2021-02-10 19:14 ` Drew Fustini
2021-02-10 19:04 ` Drew Fustini
2021-02-10 20:33 ` Dan Carpenter
2021-02-10 20:33 ` Dan Carpenter
2021-02-10 20:33 ` Dan Carpenter
2021-02-10 15:29 kernel test robot
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