From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755448AbeE2I4f (ORCPT ); Tue, 29 May 2018 04:56:35 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:16013 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751091AbeE2I4e (ORCPT ); Tue, 29 May 2018 04:56:34 -0400 Subject: Re: [PATCH v2] powerpc/64: Fix build failure with GCC 8.1 To: Geert Uytterhoeven Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Linux Kernel Mailing List , linuxppc-dev , Geoff Levand References: From: Christophe LEROY Message-ID: <1fa5b220-4d21-b4cd-33bf-8a3ce3178063@c-s.fr> Date: Tue, 29 May 2018 10:56:31 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: 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 29/05/2018 à 09:47, Geert Uytterhoeven a écrit : > Hi Christophe, > > CC Geoff > > On Tue, May 29, 2018 at 8:03 AM, Christophe Leroy > wrote: >> CC arch/powerpc/kernel/nvram_64.o >> arch/powerpc/kernel/nvram_64.c: In function 'nvram_create_partition': >> arch/powerpc/kernel/nvram_64.c:1042:2: error: 'strncpy' specified bound 12 equals destination size [-Werror=stringop-truncation] >> strncpy(new_part->header.name, name, 12); >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> CC arch/powerpc/kernel/trace/ftrace.o >> In function 'make_field', >> inlined from 'ps3_repository_read_boot_dat_address' at arch/powerpc/platforms/ps3/repository.c:900:9: >> arch/powerpc/platforms/ps3/repository.c:106:2: error: 'strncpy' output truncated before terminating nul copying 8 bytes from a string of the same length [-Werror=stringop-truncation] >> strncpy((char *)&n, text, 8); >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> Signed-off-by: Christophe Leroy > > Thanks for your patch! > >> --- a/arch/powerpc/kernel/nvram_64.c >> +++ b/arch/powerpc/kernel/nvram_64.c >> @@ -1039,7 +1039,7 @@ loff_t __init nvram_create_partition(const char *name, int sig, >> new_part->index = free_part->index; >> new_part->header.signature = sig; >> new_part->header.length = size; >> - strncpy(new_part->header.name, name, 12); >> + memcpy(new_part->header.name, name, strnlen(name, sizeof(new_part->header.name))); > > The comment for nvram_header.lgnth says: > > /* Terminating null required only for names < 12 chars. */ > > This will not terminate the string with a zero (the struct is > allocated with kmalloc). > So the original code is correct, the new one isn't. Right, then I have to first zeroize the destination. > >> new_part->header.checksum = nvram_checksum(&new_part->header); >> >> rc = nvram_write_header(new_part); >> diff --git a/arch/powerpc/platforms/ps3/repository.c b/arch/powerpc/platforms/ps3/repository.c >> index 50dbaf24b1ee..e49c887787c4 100644 >> --- a/arch/powerpc/platforms/ps3/repository.c >> +++ b/arch/powerpc/platforms/ps3/repository.c >> @@ -101,9 +101,9 @@ static u64 make_first_field(const char *text, u64 index) >> >> static u64 make_field(const char *text, u64 index) >> { >> - u64 n; >> + u64 n = 0; >> >> - strncpy((char *)&n, text, 8); >> + memcpy((char *)&n, text, strnlen(text, sizeof(n))); > > This changes behavior: strncpy() fills the remainder of the buffer with > zeroes. I don't remember the details of the PS3 repository structure, > but given this writes to a fixed size u64 buffer, I'd expect the PS3 > hypervisor code to (1) rely on the zero padding, and (2) not need a zero > terminator if there are 8 characters in the buffer, so probably the > original code is correct, and the "fixed" code isn't. Here I have set n to 0 prior to the copy, so the buffer IS zero padded. Christophe > > Has this been tested on a PS3? > >> return n + index; >> } > > Gr{oetje,eeting}s, > > Geert >