linux-kernel - Re: [PATCH] OMAP: DSS2: OMAPFB: fix potential GPF

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Message-ID: <20210626231423.GA38365@macbook.musicnaut.iki.fi>
Date:   Sun, 27 Jun 2021 02:14:23 +0300
From:   Aaro Koskinen <aaro.koskinen@....fi>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     gustavoars@...nel.org, sam@...nborg.org, tomi.valkeinen@...com,
        linux-omap@...r.kernel.org, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] OMAP: DSS2: OMAPFB: fix potential GPF

Hi,

On Sat, Jun 26, 2021 at 01:33:23AM +0300, Pavel Skripkin wrote:
> In case of allocation failures, all code paths was jumping
> to this code:
> 
> err:
> 	kfree(fbi);
> 	kfree(var);
> 	kfree(fbops);
> 
> 	return r;
> 
> Since all 3 pointers placed on stack and don't initialized, they
> will be filled with some random values, which leads to
> deferencing random pointers in kfree(). Fix it by rewriting
> error handling path.

They are initialized before the first goto:

[...]
	fbi = NULL;
	var = NULL;
	fbops = NULL;

	fbi = kzalloc(sizeof(*fbi), GFP_KERNEL);
	if (fbi == NULL) {
		r = -ENOMEM;
		goto err;
	}
[...]

A.