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@IA1PR07MB9... Kernel Branch: 6.2.0-rc5-next-20230124 Kernel config: https://drive.google.com/file/d/1F-LszDAizEEH0ZX0HcSR06v5q8FPl2Uv/view?usp=s... Reproducer: https://drive.google.com/file/d/1mP1jcLBY7vWCNM60OMf-ogw-urQRjNrm/view?usp=s...

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

---

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 mikoxyzzz@gmail.com