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From: Jiri Slaby <jirislaby@kernel.org>
To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
	gregkh@linuxfoundation.org, Daniel Vetter <daniel@ffwll.ch>,
	Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	Sanan Hasanov <sanan.hasanov@Knights.ucf.edu>
Subject: Re: [PATCH] fbcon: Check font dimension limits
Date: Thu, 26 Jan 2023 10:02:55 +0100	[thread overview]
Message-ID: <3bcd9911-5fdd-2a1a-0a76-55e1b8f7642a@kernel.org> (raw)
In-Reply-To: <20230126004921.616264824@ens-lyon.org>

On 26. 01. 23, 1:49, Samuel Thibault wrote:
> blit_x and blit_y are uint32_t, 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 <sanan.hasanov@Knights.ucf.edu>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> 
> 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 & (1U << (font->width - 1))) ||
> +	    !(info->pixmap.blit_y & (1U << (font->height - 1))))

So use BIT() properly then? That should be used in all these shifts 
anyway. Exactly to avoid UB.

thanks,
-- 
js
suse labs


WARNING: multiple messages have this Message-ID (diff)
From: Jiri Slaby <jirislaby@kernel.org>
To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
	gregkh@linuxfoundation.org, Daniel Vetter <daniel@ffwll.ch>,
	Helge Deller <deller@gmx.de>
Cc: Sanan Hasanov <sanan.hasanov@Knights.ucf.edu>,
	stable@vger.kernel.org, linux-fbdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] fbcon: Check font dimension limits
Date: Thu, 26 Jan 2023 10:02:55 +0100	[thread overview]
Message-ID: <3bcd9911-5fdd-2a1a-0a76-55e1b8f7642a@kernel.org> (raw)
In-Reply-To: <20230126004921.616264824@ens-lyon.org>

On 26. 01. 23, 1:49, Samuel Thibault wrote:
> blit_x and blit_y are uint32_t, 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 <sanan.hasanov@Knights.ucf.edu>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> 
> 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 & (1U << (font->width - 1))) ||
> +	    !(info->pixmap.blit_y & (1U << (font->height - 1))))

So use BIT() properly then? That should be used in all these shifts 
anyway. Exactly to avoid UB.

thanks,
-- 
js
suse labs


  parent reply	other threads:[~2023-01-26  9:03 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20230126004911.869923511@ens-lyon.org>
2023-01-26  0:49 ` [PATCH] fbcon: Check font dimension limits Samuel Thibault
2023-01-26  0:49   ` Samuel Thibault
2023-01-26  0:51   ` Samuel Thibault
2023-01-26  0:51     ` Samuel Thibault
2023-01-26  7:43   ` Greg KH
2023-01-26  7:43     ` Greg KH
2023-01-26  9:08     ` Jiri Slaby
2023-01-26  9:08       ` Jiri Slaby
2023-01-29 15:13     ` Samuel Thibault
2023-01-29 15:13       ` Samuel Thibault
2023-01-26  9:02   ` Jiri Slaby [this message]
2023-01-26  9:02     ` Jiri Slaby
2023-01-29 15:04     ` Samuel Thibault
2023-01-29 15:04       ` Samuel Thibault
2023-01-28  1:32   ` kernel test robot

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