From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752133AbeBZGfD (ORCPT ); Mon, 26 Feb 2018 01:35:03 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:2557 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750982AbeBZGfC (ORCPT ); Mon, 26 Feb 2018 01:35:02 -0500 Subject: Re: [PATCH 06/21] powerpc: Avoid comparison of unsigned long >= 0 in __access_ok To: Mathieu Malaterre , Michael Ellerman Cc: linux-kernel@vger.kernel.org, Paul Mackerras , Jiri Slaby , linuxppc-dev@lists.ozlabs.org References: <20180225172236.29650-1-malat@debian.org> <20180225172236.29650-7-malat@debian.org> From: Christophe LEROY Message-ID: <8862c1e1-d161-3410-1b2a-502ad06cef57@c-s.fr> Date: Mon, 26 Feb 2018 07:34:59 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180225172236.29650-7-malat@debian.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 25/02/2018 à 18:22, Mathieu Malaterre a écrit : > Rewrite check size - 1 <= Y as size < Y since `size` is unsigned value. > Fix warning (treated as error in W=1): > > CC arch/powerpc/kernel/signal_32.o > In file included from ./include/linux/uaccess.h:14:0, > from ./include/asm-generic/termios-base.h:8, > from ./arch/powerpc/include/asm/termios.h:20, > from ./include/uapi/linux/termios.h:6, > from ./include/linux/tty.h:7, > from arch/powerpc/kernel/signal_32.c:36: > ./include/asm-generic/termios-base.h: In function ‘user_termio_to_kernel_termios’: > ./arch/powerpc/include/asm/uaccess.h:52:35: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits] > (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr))))) > ^ > ./arch/powerpc/include/asm/uaccess.h:58:3: note: in expansion of macro ‘__access_ok’ > __access_ok((__force unsigned long)(addr), (size), get_fs())) > ^~~~~~~~~~~ > ./arch/powerpc/include/asm/uaccess.h:262:6: note: in expansion of macro ‘access_ok’ > if (access_ok(VERIFY_READ, __gu_addr, (size))) \ > ^~~~~~~~~ > ./arch/powerpc/include/asm/uaccess.h:80:2: note: in expansion of macro ‘__get_user_check’ > __get_user_check((x), (ptr), sizeof(*(ptr))) > ^~~~~~~~~~~~~~~~ > ./include/asm-generic/termios-base.h:36:6: note: in expansion of macro ‘get_user’ > if (get_user(termios->c_line, &termio->c_line) < 0) > ^~~~~~~~ > [...] > cc1: all warnings being treated as errors > > Signed-off-by: Mathieu Malaterre > --- > arch/powerpc/include/asm/uaccess.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h > index 51bfeb8777f0..fadc406bd39d 100644 > --- a/arch/powerpc/include/asm/uaccess.h > +++ b/arch/powerpc/include/asm/uaccess.h > @@ -49,7 +49,7 @@ > > #define __access_ok(addr, size, segment) \ > (((addr) <= (segment).seg) && \ > - (((size) == 0) || (((size) - 1) <= ((segment).seg - (addr))))) > + (((size) == 0) || ((size) < ((segment).seg - (addr))))) IIUC, ((2 - 1) <= 1) is the same as (2 < 1) ????? Christophe > > #endif > >