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 <sanan.hasanov@Knights.ucf.edu>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Fixes: 2d2699d98492 ("fbcon: font setting should check limitation of driver")
Cc: stable@vger.kernel.org
Tested-by: Miko Larsson <mikoxyzzz@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 14a7d404062c38e006933da5d42a729b8f9fbf07..1b14c21af2b74983f02dd17dbf99bae8a249e25f 100644 (file)
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2495,9 +2495,12 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font,
            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 */