From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id D55892036B for ; Wed, 4 Oct 2017 05:58:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751047AbdJDF6R (ORCPT ); Wed, 4 Oct 2017 01:58:17 -0400 Received: from bsmtp7.bon.at ([213.33.87.19]:23518 "EHLO bsmtp7.bon.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797AbdJDF6R (ORCPT ); Wed, 4 Oct 2017 01:58:17 -0400 Received: from dx.site (unknown [93.83.142.38]) by bsmtp7.bon.at (Postfix) with ESMTPSA id 3y6QDl0ZhHz5tlP; Wed, 4 Oct 2017 07:58:14 +0200 (CEST) Received: from [IPv6:::1] (localhost [IPv6:::1]) by dx.site (Postfix) with ESMTP id 4731F2127; Wed, 4 Oct 2017 07:58:14 +0200 (CEST) Subject: Re: [PATCH 3/3] sub-process: allocate argv on the heap To: Junio C Hamano Cc: Thomas Gummerer , git@vger.kernel.org, Lars Schneider , Ben Peart , Ben Peart , =?UTF-8?Q?Jakub_Nar=c4=99bski?= References: <20171003195713.13395-1-t.gummerer@gmail.com> <20171003195713.13395-4-t.gummerer@gmail.com> <85456f81-9e9f-d0e4-86f7-9f546691dee3@kdbg.org> From: Johannes Sixt Message-ID: Date: Wed, 4 Oct 2017 07:58:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Am 04.10.2017 um 06:59 schrieb Junio C Hamano: > Johannes Sixt writes: > >> Am 03.10.2017 um 21:57 schrieb Thomas Gummerer: >>> diff --git a/sub-process.c b/sub-process.c >>> index 6dde5062be..4680af8193 100644 >>> --- a/sub-process.c >>> +++ b/sub-process.c >>> @@ -77,7 +77,9 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co >>> { >>> int err; >>> struct child_process *process; >>> - const char *argv[] = { cmd, NULL }; >>> + const char **argv = xmalloc(2 * sizeof(char *)); >>> + argv[0] = cmd; >>> + argv[1] = NULL; >>> entry->cmd = cmd; >>> process = &entry->process; >>> >> >> Perhaps this should become >> >> argv_array_push(&process->args, cmd); >> >> so that there is no new memory leak? > > Sounds like a good idea (if I am not grossly mistaken as to what is > being suggested). > > Here is what I am planning to queue. > > -- >8 -- > From: Johannes Sixt > Date: Tue, 3 Oct 2017 22:24:57 +0200 > Subject: [PATCH] sub-process: use child_process.args instead of child_process.argv > > Currently the argv is only allocated on the stack, and then assigned to > process->argv. When the start_subprocess function goes out of scope, > the local argv variable is eliminated from the stack, but the pointer is > still kept around in process->argv. > > Much later when we try to access the same process->argv in > finish_command, this leads us to access a memory location that no longer > contains what we want. As argv0 is only used for printing errors, this > is not easily noticed in normal git operations. However when running > t0021-conversion.sh through valgrind, valgrind rightfully complains: > > ==21024== Invalid read of size 8 > ==21024== at 0x2ACF64: finish_command (run-command.c:869) > ==21024== by 0x2D6B18: subprocess_exit_handler (sub-process.c:72) > ==21024== by 0x2AB41E: cleanup_children (run-command.c:45) > ==21024== by 0x2AB526: cleanup_children_on_exit (run-command.c:81) > ==21024== by 0x54AD487: __run_exit_handlers (in /usr/lib/libc-2.26.so) > ==21024== by 0x54AD4D9: exit (in /usr/lib/libc-2.26.so) > ==21024== by 0x11A9EF: handle_builtin (git.c:550) > ==21024== by 0x11ABCC: run_argv (git.c:602) > ==21024== by 0x11AD8E: cmd_main (git.c:679) > ==21024== by 0x1BF125: main (common-main.c:43) > ==21024== Address 0x1ffeffec00 is on thread 1's stack > ==21024== 1504 bytes below stack pointer > ==21024== > > These days, the child_process structure has its own args array, and > the standard way to set up its argv[] is to use that one, instead of > assigning to process->argv to point at an array that is outside. > Use that facility automatically fixes this issue. > > Reported-by: Thomas Gummerer > Signed-off-by: Johannes Sixt > Signed-off-by: Junio C Hamano > --- > sub-process.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/sub-process.c b/sub-process.c > index fcc4832c14..648b3a3943 100644 > --- a/sub-process.c > +++ b/sub-process.c > @@ -74,13 +74,12 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co > { > int err; > struct child_process *process; > - const char *argv[] = { cmd, NULL }; > > entry->cmd = cmd; > process = &entry->process; > > child_process_init(process); > - process->argv = argv; > + argv_array_push(&process->args, cmd); > process->use_shell = 1; > process->in = -1; > process->out = -1; > Thank you very much! That looks good. Just to be on the safe side: Signed-off-by: Johannes Sixt -- Hannes