linux-kernel - Re: [PATCH v1 1/4] auxdisplay: hd44780: Fix memory leak on ->remove()

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Date:   Tue, 12 Mar 2019 14:47:01 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        Willy Tarreau <willy@...roxy.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/4] auxdisplay: hd44780: Fix memory leak on ->remove()

Hi Andy,

On Tue, Mar 12, 2019 at 2:18 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> We have to free on ->remove() the allocated resources on ->probe().
>
> Fixes: d47d88361fee ("auxdisplay: Add HD44780 Character LCD support")
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Thanks, nice catch!

> --- a/drivers/auxdisplay/hd44780.c
> +++ b/drivers/auxdisplay/hd44780.c
> @@ -280,6 +280,8 @@ static int hd44780_remove(struct platform_device *pdev)
>         struct charlcd *lcd = platform_get_drvdata(pdev);
>
>         charlcd_unregister(lcd);
> +
> +       kfree(lcd);

(wearing a newer (and hopefully wiser ;-) hat than when I wrote the code)

While this is correct for the current implementation of struct charlcd_priv,
this may be a bit fragile.

What about adding a charlcd_free() wrapper, which can do kfree(to_priv(lcd)),
and be used in the probe failure path, too?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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