Re: [PATCH] fbcon: Check font dimension limits
From: Greg KH <gregkh@linuxfoundation.org>
Date: 2023-01-26 07:43:11
Also in:
dri-devel, lkml, stable
On Thu, Jan 26, 2023 at 01:49:12AM +0100, Samuel Thibault wrote:
blit_x and blit_y are uint32_t, so fbcon currently cannot support fonts larger than 32x32.
"u32" you mean, right?
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 (local)
Odd blank line?
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
What are all of these lines for?
Reported-by: Sanan Hasanov <redacted> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
What commit id does this fix? Should it go to stable kernels?
quoted hunk ↗ jump to hunk
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))))
Are you sure this is still needed with the above check added? If so, why? What is the difference in the compiled code? thanks, greg k-h