linux-kernel - Re: [PATCH] video: hgafb: correctly handle card detect failure during probe

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Message-ID: <2b945eaa-4288-1601-3f1a-60f2ceaa1ea7@gmail.com>
Date:   Mon, 17 May 2021 09:27:38 -0300
From:   Igor Torrente <igormtorrente@...il.com>
To:     Anirudh Rayabharam <mail@...rudhrb.com>,
        Ferenc Bakonyi <fero@...ma.obuda.kando.hu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        kernel test robot <oliver.sang@...el.com>,
        stable <stable@...r.kernel.org>,
        linux-nvidia@...ts.surfsouth.com, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] video: hgafb: correctly handle card detect failure during
 probe

Hi,

On 5/16/21 4:27 PM, Anirudh Rayabharam wrote:
> The return value of hga_card_detect() is not properly handled causing
> the probe to succeed even though hga_card_detect() failed. Since probe
> succeeds, hgafb_open() can be called which will end up operating on an
> unmapped hga_vram. This results in an out-of-bounds access as reported
> by kernel test robot [1].
> 
> To fix this, correctly detect failure of hga_card_detect() by checking
> for a non-zero error code.
> 
> [1]: https://lore.kernel.org/lkml/20210516150019.GB25903@xsang-OptiPlex-9020/
> 
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Fixes: dc13cac4862c ("video: hgafb: fix potential NULL pointer dereference")
> Cc: stable <stable@...r.kernel.org>
> Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.com>
> ---
>   drivers/video/fbdev/hgafb.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/hgafb.c b/drivers/video/fbdev/hgafb.c
> index cc8e62ae93f6..bd3d07aa4f0e 100644
> --- a/drivers/video/fbdev/hgafb.c
> +++ b/drivers/video/fbdev/hgafb.c
> @@ -558,7 +558,7 @@ static int hgafb_probe(struct platform_device *pdev)
>   	int ret;
>   
>   	ret = hga_card_detect();
> -	if (!ret)
> +	if (ret)
>   		return ret;
>   
>   	printk(KERN_INFO "hgafb: %s with %ldK of memory detected.\n",
> 

In fact, this return isn't being properly handled. Thanks for fix it!

Reviewed-by: Igor Matheus Andrade Torrente <igormtorrente@...il.com>