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

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Message-ID: <YKZm17dj4R1c2ns/@anirudhrb.com>
Date:   Thu, 20 May 2021 19:10:39 +0530
From:   Anirudh Rayabharam <mail@...rudhrb.com>
To:     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,
        mail@...rudhrb.com, igormtorrente@...il.com,
        fero@...ma.obuda.kando.hu
Subject: Re: [PATCH] video: hgafb: correctly handle card detect failure
 during probe

On Mon, May 17, 2021 at 12:57:14AM +0530, 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")

Greg, this is one of the UMN fixes we did. So, do you want to take this
patch into your tree?

thanks!

	- Anirudh.

> 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",
> -- 
> 2.26.2
>