linux-kernel - Re: [PATCHv2] fbcon: Check font dimension limits

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Message-ID: <Y9kq4ZoBs8LkEtqs@kroah.com>
Date:   Tue, 31 Jan 2023 15:51:13 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Samuel Thibault <samuel.thibault@...-lyon.org>,
        Daniel Vetter <daniel@...ll.ch>, Helge Deller <deller@....de>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sanan Hasanov <sanan.hasanov@...ghts.ucf.edu>
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 <sanan.hasanov@...ghts.ucf.edu>
> Signed-off-by: Samuel Thibault <samuel.thibault@...-lyon.org>
> Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of driver")
> Cc: stable@...r.kernel.org

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>