Greg KH, le jeu. 26 janv. 2023 08:43:02 +0100, a ecrit: > 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? 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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > > Odd blank line? Not sure what you mean? I found it easier to read to put a blank line between the text and the references. > > 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? They provide the references that were set in the original report http://lore.kernel.org/all/IA1PR07MB98308653E259A6F2CE94A4AFABCE9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Arguably the "branch" and "config" are not that useful since the bug has been there for more than a dozen years, but notably the "Reproducer" is useful to provide a userland program that triggers the UB. > > Reported-by: Sanan Hasanov <sanan.hasanov@xxxxxxxxxxxxxxx> > > Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> > > What commit id does this fix? I though it was there forever, but it seems the check was added in 2007, so I'll add it in next version. > Should it go to stable kernels? Yes. I added stable in Cc of the mail but missed adding it in the text, I will add it. > > 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? As mentioned by Jiri, yes in the 32 case it's needed otherwise it's UB. Samuel
