[v2] video: imsttfb: Fix use after free bug in imsttfb_probe due to lack of error-handling of init_imstt

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

Posted by Zheng Wang 2 years, 7 months ago

A use-after-free bug may occur if init_imstt invokes framebuffer_release
and free the info ptr. The caller, imsttfb_probe didn't notice that and
still keep the ptr as private data in pdev.

If we remove the driver which will call imsttfb_remove to make cleanup,
UAF happens.

Fix it by return error code if bad case happens in init_imstt.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
---
v2:
- add return error code in another location.
---
 drivers/video/fbdev/imsttfb.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/video/fbdev/imsttfb.c b/drivers/video/fbdev/imsttfb.c
index bea45647184e..975dd682fae4 100644
--- a/drivers/video/fbdev/imsttfb.c
+++ b/drivers/video/fbdev/imsttfb.c
@@ -1347,7 +1347,7 @@ static const struct fb_ops imsttfb_ops = {
 	.fb_ioctl 	= imsttfb_ioctl,
 };
 
-static void init_imstt(struct fb_info *info)
+static int init_imstt(struct fb_info *info)
 {
 	struct imstt_par *par = info->par;
 	__u32 i, tmp, *ip, *end;
@@ -1420,7 +1420,7 @@ static void init_imstt(struct fb_info *info)
 	    || !(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;
+		return -ENODEV;
 	}
 
 	sprintf(info->fix.id, "IMS TT (%s)", par->ramdac == IBM ? "IBM" : "TVP");
@@ -1456,12 +1456,13 @@ static void init_imstt(struct fb_info *info)
 
 	if (register_framebuffer(info) < 0) {
 		framebuffer_release(info);
-		return;
+		return -ENODEV;
 	}
 
 	tmp = (read_reg_le32(par->dc_regs, SSTATUS) & 0x0f00) >> 8;
 	fb_info(info, "%s frame buffer; %uMB vram; chip version %u\n",
 		info->fix.id, info->fix.smem_len >> 20, tmp);
+	return 0;
 }
 
 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)
-- 
2.25.1

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

Posted by Michal Koutný 2 years, 6 months ago

Hello.

On Thu, Apr 27, 2023 at 11:08:41AM +0800, Zheng Wang <zyytlz.wz@163.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:

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

Posted by Helge Deller 2 years, 6 months ago

Hi Michal,

On 5/22/23 17:36, Michal Koutný wrote:
> On Thu, Apr 27, 2023 at 11:08:41AM +0800, Zheng Wang <zyytlz.wz@163.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.)

Yes, you seem to be right.

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

Yes, but ....


> 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);

That's ^^^  ok, but I think a
	fb_dealloc_cmap()
is missing here ...

... and in the error path of imsttfb_probe() ....

>   		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:

Would you mind sending a proper patch?

Thanks for noticing!
Helge

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

Posted by Helge Deller 2 years, 7 months ago

On 4/27/23 05:08, Zheng Wang wrote:
> A use-after-free bug may occur if init_imstt invokes framebuffer_release
> and free the info ptr. The caller, imsttfb_probe didn't notice that and
> still keep the ptr as private data in pdev.
>
> If we remove the driver which will call imsttfb_remove to make cleanup,
> UAF happens.
>
> Fix it by return error code if bad case happens in init_imstt.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>

applied.
Thanks!
Helge

> ---
> v2:
> - add return error code in another location.
> ---
>   drivers/video/fbdev/imsttfb.c | 15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/video/fbdev/imsttfb.c b/drivers/video/fbdev/imsttfb.c
> index bea45647184e..975dd682fae4 100644
> --- a/drivers/video/fbdev/imsttfb.c
> +++ b/drivers/video/fbdev/imsttfb.c
> @@ -1347,7 +1347,7 @@ static const struct fb_ops imsttfb_ops = {
>   	.fb_ioctl 	= imsttfb_ioctl,
>   };
>
> -static void init_imstt(struct fb_info *info)
> +static int init_imstt(struct fb_info *info)
>   {
>   	struct imstt_par *par = info->par;
>   	__u32 i, tmp, *ip, *end;
> @@ -1420,7 +1420,7 @@ static void init_imstt(struct fb_info *info)
>   	    || !(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;
> +		return -ENODEV;
>   	}
>
>   	sprintf(info->fix.id, "IMS TT (%s)", par->ramdac == IBM ? "IBM" : "TVP");
> @@ -1456,12 +1456,13 @@ static void init_imstt(struct fb_info *info)
>
>   	if (register_framebuffer(info) < 0) {
>   		framebuffer_release(info);
> -		return;
> +		return -ENODEV;
>   	}
>
>   	tmp = (read_reg_le32(par->dc_regs, SSTATUS) & 0x0f00) >> 8;
>   	fb_info(info, "%s frame buffer; %uMB vram; chip version %u\n",
>   		info->fix.id, info->fix.smem_len >> 20, tmp);
> +	return 0;
>   }
>
>   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)