linux-kernel - Re: [PATCH] video: smscufx: Fix null-ptr-deref in ufx_usb

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Message-ID: <8742cda5-1fc7-ae44-076c-e4a522ca43f5@suse.de>
Date:   Thu, 14 Oct 2021 15:58:37 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Wang Hai <wanghai38@...wei.com>, steve.glendinning@...well.net,
        FlorianSchandinat@....de, gregkh@...e.de
Cc:     linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] video: smscufx: Fix null-ptr-deref in ufx_usb_probe()

Hi

Am 14.10.21 um 15:22 schrieb Wang Hai:
> I got a null-ptr-deref report:
> 
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> ...
> RIP: 0010:fb_destroy_modelist+0x38/0x100
> ...
> Call Trace:
>   ufx_usb_probe.cold+0x2b5/0xac1 [smscufx]
>   usb_probe_interface+0x1aa/0x3c0 [usbcore]
>   really_probe+0x167/0x460
> ...
>   ret_from_fork+0x1f/0x30
> 
> If fb_alloc_cmap() fails in ufx_usb_probe(), fb_destroy_modelist() will
> be called to destroy modelist in the error handling path. But modelist
> has not been initialized yet, so it will result in null-ptr-deref.
> 
> Initialize modelist before calling fb_alloc_cmap() to fix this bug.
> 
> Fixes: 3c8a63e22a08 ("Add support for SMSC UFX6000/7000 USB display adapters")
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Wang Hai <wanghai38@...wei.com>

Acked-by: Thomas Zimmermann <tzimmermann@...e.de>

I got one of these devices but the driver didn't produce any output for 
me. Are actually able to use the driver?

Best regards
Thomas

> ---
>   drivers/video/fbdev/smscufx.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c
> index bfac3ee4a642..28768c272b73 100644
> --- a/drivers/video/fbdev/smscufx.c
> +++ b/drivers/video/fbdev/smscufx.c
> @@ -1656,6 +1656,7 @@ static int ufx_usb_probe(struct usb_interface *interface,
>   	info->par = dev;
>   	info->pseudo_palette = dev->pseudo_palette;
>   	info->fbops = &ufx_ops;
> +	INIT_LIST_HEAD(&info->modelist);
>   
>   	retval = fb_alloc_cmap(&info->cmap, 256, 0);
>   	if (retval < 0) {
> @@ -1666,8 +1667,6 @@ static int ufx_usb_probe(struct usb_interface *interface,
>   	INIT_DELAYED_WORK(&dev->free_framebuffer_work,
>   			  ufx_free_framebuffer_work);
>   
> -	INIT_LIST_HEAD(&info->modelist);
> -
>   	retval = ufx_reg_read(dev, 0x3000, &id_rev);
>   	check_warn_goto_error(retval, "error %d reading 0x3000 register from device", retval);
>   	dev_dbg(dev->gdev, "ID_REV register value 0x%08x", id_rev);
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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