linux-kernel - Re: [PATCH] lkdtm: cfi: Fix type width for masking PAC bits

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Date:   Wed, 27 Apr 2022 15:39:04 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     kernel test robot <lkp@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dan Li <ashimida@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] lkdtm: cfi: Fix type width for masking PAC bits



On 4/26/22 17:12, Kees Cook 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>

Tested-by: Randy Dunlap <rdunlap@...radead.org>
fwiw
Thanks.

> ---
>  drivers/misc/lkdtm/cfi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c
> index 804965a480b7..666a7f4bc137 100644
> --- 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))
>  
>  /* The ultimate ROP gadget. */
>  static noinline __no_ret_protection

-- 
~Randy