(FYI, the UB was already a problem before my big-font patch submission, the checks I add here are already making sense in previous versions anyway)
Samuel Thibault, le jeu. 26 janv. 2023 01:49:12 +0100, a ecrit: > blit_x and blit_y are uint32_t, 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/ia1pr07mb98308653e259a6f2ce94a4afab...@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.hasa...@knights.ucf.edu> > Signed-off-by: Samuel Thibault <samuel.thiba...@ens-lyon.org> > > 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)))) > return -EINVAL; > > /* Make sure driver can handle the font length */ > >
