2023-01-29 15:17:47

by Samuel Thibault

Subject: [PATCHv2] fbcon: Check font dimension limits

blit_x and blit_y are u32, so fbcon currently cannot support fonts
larger than 32x32.

The 32x32 case also needs shifting an unsigned int, to properly set bit
31, otherwise we get "UBSAN: shift-out-of-bounds in fbcon_set_font",
as reported on:

http://lore.kernel.org/all/IA1PR07MB98308653E259A6F2CE94A4AFABCE9@IA1PR07MB9830.namprd07.prod.outlook.com
Kernel Branch: 6.2.0-rc5-next-20230124
Kernel config: https://drive.google.com/file/d/1F-LszDAizEEH0ZX0HcSR06v5q8FPl2Uv/view?usp=sharing
Reproducer: https://drive.google.com/file/d/1mP1jcLBY7vWCNM60OMf-ogw-urQRjNrm/view?usp=sharing

Reported-by: Sanan Hasanov <[email protected]>
Signed-off-by: Samuel Thibault <[email protected]>
Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of driver")
Cc: [email protected]

---
v1 -> v2:
- Use BIT macro instead of fixing bit test by hand.
- Add Fixes and Cc: stable headers.

Index: linux-6.0/drivers/video/fbdev/core/fbcon.c
===================================================================
--- linux-6.0.orig/drivers/video/fbdev/core/fbcon.c
+++ linux-6.0/drivers/video/fbdev/core/fbcon.c
@@ -2489,9 +2489,12 @@ static int fbcon_set_font(struct vc_data
h > FBCON_SWAP(info->var.rotate, info->var.yres, info->var.xres))
return -EINVAL;

+ if (font->width > 32 || font->height > 32)
+ return -EINVAL;
+
/* Make sure drawing engine can handle the font */
- if (!(info->pixmap.blit_x & (1 << (font->width - 1))) ||
- !(info->pixmap.blit_y & (1 << (font->height - 1))))
+ if (!(info->pixmap.blit_x & BIT(font->width - 1)) ||
+ !(info->pixmap.blit_y & BIT(font->height - 1)))
return -EINVAL;

/* Make sure driver can handle the font length */

2023-01-29 17:09:12

by Miko Larsson

Subject: Re: [PATCHv2] fbcon: Check font dimension limits

On Sun, 2023-01-29 at 16:17 +0100, Samuel Thibault wrote:
> blit_x and blit_y are u32, so fbcon currently cannot support fonts
> larger than 32x32.
>
> The 32x32 case also needs shifting an unsigned int, to properly set
> bit
> 31, otherwise we get "UBSAN: shift-out-of-bounds in fbcon_set_font",
> as reported on:
>
> http://lore.kernel.org/all/IA1PR07MB98308653E259A6F2CE94A4AFABCE9@IA1PR07MB9830.namprd07.prod.outlook.com
> Kernel Branch: 6.2.0-rc5-next-20230124
> Kernel config:
> https://drive.google.com/file/d/1F-LszDAizEEH0ZX0HcSR06v5q8FPl2Uv/view?usp=sharing
> Reproducer:
> https://drive.google.com/file/d/1mP1jcLBY7vWCNM60OMf-ogw-urQRjNrm/view?usp=sharing
>
> Reported-by: Sanan Hasanov <[email protected]>
> Signed-off-by: Samuel Thibault <[email protected]>
> Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of
> driver")
> Cc: [email protected]
>
> ---
> v1 -> v2:
> - Use BIT macro instead of fixing bit test by hand.
> - Add Fixes and Cc: stable headers.
>
> Index: linux-6.0/drivers/video/fbdev/core/fbcon.c
> ===================================================================
> --- linux-6.0.orig/drivers/video/fbdev/core/fbcon.c
> +++ linux-6.0/drivers/video/fbdev/core/fbcon.c
> @@ -2489,9 +2489,12 @@ static int fbcon_set_font(struct vc_data
>             h > FBCON_SWAP(info->var.rotate, info->var.yres, info-
> >var.xres))
>                 return -EINVAL;
>  
> +       if (font->width > 32 || font->height > 32)
> +               return -EINVAL;
> +
>         /* Make sure drawing engine can handle the font */
> -       if (!(info->pixmap.blit_x & (1 << (font->width - 1))) ||
> -           !(info->pixmap.blit_y & (1 << (font->height - 1))))
> +       if (!(info->pixmap.blit_x & BIT(font->width - 1)) ||
> +           !(info->pixmap.blit_y & BIT(font->height - 1)))
>                 return -EINVAL;
>  
>         /* Make sure driver can handle the font length */

Tested-by: Miko Larsson <[email protected]>
--
~miko

2023-01-31 14:51:24

by Greg Kroah-Hartman

Subject: Re: [PATCHv2] fbcon: Check font dimension limits

On Sun, Jan 29, 2023 at 04:17:40PM +0100, Samuel Thibault wrote:
> blit_x and blit_y are u32, so fbcon currently cannot support fonts
> larger than 32x32.
>
> The 32x32 case also needs shifting an unsigned int, to properly set bit
> 31, otherwise we get "UBSAN: shift-out-of-bounds in fbcon_set_font",
> as reported on:
>
> http://lore.kernel.org/all/IA1PR07MB98308653E259A6F2CE94A4AFABCE9@IA1PR07MB9830.namprd07.prod.outlook.com
> Kernel Branch: 6.2.0-rc5-next-20230124
> Kernel config: https://drive.google.com/file/d/1F-LszDAizEEH0ZX0HcSR06v5q8FPl2Uv/view?usp=sharing
> Reproducer: https://drive.google.com/file/d/1mP1jcLBY7vWCNM60OMf-ogw-urQRjNrm/view?usp=sharing
>
> Reported-by: Sanan Hasanov <[email protected]>
> Signed-off-by: Samuel Thibault <[email protected]>
> Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of driver")
> Cc: [email protected]

Reviewed-by: Greg Kroah-Hartman <[email protected]>

2023-02-04 13:32:55

by Helge Deller

Subject: Re: [PATCHv2] fbcon: Check font dimension limits

On 1/31/23 15:51, Greg KH wrote:
> On Sun, Jan 29, 2023 at 04:17:40PM +0100, Samuel Thibault wrote:
>> blit_x and blit_y are u32, so fbcon currently cannot support fonts
>> larger than 32x32.
>>
>> The 32x32 case also needs shifting an unsigned int, to properly set bit
>> 31, otherwise we get "UBSAN: shift-out-of-bounds in fbcon_set_font",
>> as reported on:
>>
>> http://lore.kernel.org/all/IA1PR07MB98308653E259A6F2CE94A4AFABCE9@IA1PR07MB9830.namprd07.prod.outlook.com
>> Kernel Branch: 6.2.0-rc5-next-20230124
>> Kernel config: https://drive.google.com/file/d/1F-LszDAizEEH0ZX0HcSR06v5q8FPl2Uv/view?usp=sharing
>> Reproducer: https://drive.google.com/file/d/1mP1jcLBY7vWCNM60OMf-ogw-urQRjNrm/view?usp=sharing
>>
>> Reported-by: Sanan Hasanov <[email protected]>
>> Signed-off-by: Samuel Thibault <[email protected]>
>> Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of driver")
>> Cc: [email protected]
>
> Reviewed-by: Greg Kroah-Hartman <[email protected]>

applied to fbdev git tree.

Thanks!
Helge