linux-kernel - Re: [PATCH] [video/fbdev] mbxfb_remove: fix null pointer dereference

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Date:   Sun, 26 Jul 2020 11:57:00 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Gaurav Singh <gaurav1086@...il.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Arnd Bergmann <arnd@...db.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jani Nikula <jani.nikula@...el.com>,
        "open list:FRAMEBUFFER LAYER" <dri-devel@...ts.freedesktop.org>,
        "open list:FRAMEBUFFER LAYER" <linux-fbdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [video/fbdev] mbxfb_remove: fix null pointer dereference

On Sun, Jul 26, 2020 at 8:26 AM Gaurav Singh <gaurav1086@...il.com> wrote:
>
> Function mbxfb_debugfs_remove() accesses fbi->par without NULL check,
> hence do the NULL check in the caller mbxfb_remove().

...

> @@ -1012,11 +1012,10 @@ static int mbxfb_remove(struct platform_device *dev)
>
>         write_reg_dly(SYSRST_RST, SYSRST);
>
> -       mbxfb_debugfs_remove(fbi);
> -

>         if (fbi) {

Can you explain how this is NULL on ->remove()?

I bet this check is simply redundant. But you have to check and update
commit message accordingly.

>                 struct mbxfb_info *mfbi = fbi->par;
>
> +               mbxfb_debugfs_remove(fbi);
>                 unregister_framebuffer(fbi);
>                 if (mfbi) {
>                         if (mfbi->platform_remove)


-- 
With Best Regards,
Andy Shevchenko