linux-kernel - Re: [PATCH v2] video: imsttfb: Fix use after free bug in imsttfb_probe due to lack of error-handling of init

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Message-ID: <34gbv2k3lc5dl4nbivslizfuor6qc34j63idiiuc35qkk3iohs@7bshmqu2ue7a>
Date:   Mon, 22 May 2023 17:36:14 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     deller@....de, alex000young@...il.com, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, hackerzheng666@...il.com,
        dri-devel@...ts.freedesktop.org, javierm@...hat.com,
        1395428693sheep@...il.com, tzimmermann@...e.de
Subject: Re: [PATCH v2] video: imsttfb: Fix use after free bug in
 imsttfb_probe due to lack of error-handling of init_imstt

Hello.

On Thu, Apr 27, 2023 at 11:08:41AM +0800, Zheng Wang <zyytlz.wz@....com> wrote:
>  static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> @@ -1529,10 +1530,10 @@ static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	if (!par->cmap_regs)
>  		goto error;
>  	info->pseudo_palette = par->palette;
> -	init_imstt(info);
> -
> -	pci_set_drvdata(pdev, info);
> -	return 0;
> +	ret = init_imstt(info);
> +	if (!ret)
> +		pci_set_drvdata(pdev, info);
> +	return ret;
>  
>  error:
>  	if (par->dc_regs)

This part caught my eye -- shouldn't the -ENODEV from init_imstt go
through the standard error with proper cleanup? (It seems like a leak
from my 30000 ft view, i.e. not sure about imsttfb_{probe,remove}
pairing.)

Shouldn't there be something like the diff below on top of the existing code?

Regards,
Michal

diff --git a/drivers/video/fbdev/imsttfb.c b/drivers/video/fbdev/imsttfb.c
index 975dd682fae4..a116ac8ca020 100644
--- a/drivers/video/fbdev/imsttfb.c
+++ b/drivers/video/fbdev/imsttfb.c
@@ -1419,7 +1419,6 @@ static int init_imstt(struct fb_info *info)
 	if ((info->var.xres * info->var.yres) * (info->var.bits_per_pixel >> 3) > info->fix.smem_len
 	    || !(compute_imstt_regvals(par, info->var.xres, info->var.yres))) {
 		printk("imsttfb: %ux%ux%u not supported\n", info->var.xres, info->var.yres, info->var.bits_per_pixel);
-		framebuffer_release(info);
 		return -ENODEV;
 	}
 
@@ -1455,7 +1454,6 @@ static int init_imstt(struct fb_info *info)
 	fb_alloc_cmap(&info->cmap, 0, 0);
 
 	if (register_framebuffer(info) < 0) {
-		framebuffer_release(info);
 		return -ENODEV;
 	}
 
@@ -1531,8 +1529,10 @@ static int imsttfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		goto error;
 	info->pseudo_palette = par->palette;
 	ret = init_imstt(info);
-	if (!ret)
-		pci_set_drvdata(pdev, info);
+	if (ret)
+		goto error;
+
+	pci_set_drvdata(pdev, info);
 	return ret;
 
 error:



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