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Date: Wed, 27 Apr 2022 09:14:10 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Kees Cook <keescook@...omium.org> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, kernel test robot <lkp@...el.com>, Arnd Bergmann <arnd@...db.de>, Dan Li <ashimida@...ux.alibaba.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-hardening@...r.kernel.org Subject: Re: [PATCH] lkdtm: cfi: Fix type width for masking PAC bits Hi Kees, On Wed, Apr 27, 2022 at 2:12 AM Kees Cook <keescook@...omium.org> wrote: > The masking for PAC bits wasn't handling 32-bit architectures correctly. > Replace the u64 cast with uintptr_t. > > Reported-by: kernel test robot <lkp@...el.com> > Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org> > Link: https://lore.kernel.org/lkml/CAMuHMdVz-J-1ZQ08u0bsQihDkcRmEPrtX5B_oRJ+Ns5jrasnUw@mail.gmail.com > Fixes: 2e53b877dc12 ("lkdtm: Add CFI_BACKWARD to test ROP mitigations") > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> > Cc: Arnd Bergmann <arnd@...db.de> > Signed-off-by: Kees Cook <keescook@...omium.org> Thank you, that fixes the m68k allmodconfig build, so Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org> > --- a/drivers/misc/lkdtm/cfi.c > +++ b/drivers/misc/lkdtm/cfi.c > @@ -59,7 +59,7 @@ static void lkdtm_CFI_FORWARD_PROTO(void) > #endif > > #define no_pac_addr(addr) \ > - ((__force __typeof__(addr))((__force u64)(addr) | PAGE_OFFSET)) > + ((__force __typeof__(addr))((uintptr_t)(addr) | PAGE_OFFSET)) Not related to this patch, but "| PAGE_OFFSET" is not identical to "+ PAGE_OFFSET" for large kernel sizes. More specifically, I'm thinking about platforms where "large" would be >= 32 MiB: arch/mips/include/asm/mach-ar7/spaces.h:#define PAGE_OFFSET _AC(0x94000000, UL) or >= 128 MiB: arch/x86/Kconfig: default 0x78000000 if VMSPLIT_2G_OPT Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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