From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.2 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by inbox.vuxu.org (OpenSMTPD) with SMTP id e1c43035 for ; Sat, 8 Feb 2020 16:19:23 +0000 (UTC) Received: (qmail 11739 invoked by uid 550); 8 Feb 2020 16:19:22 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 11721 invoked from network); 8 Feb 2020 16:19:21 -0000 Date: Sat, 8 Feb 2020 11:19:08 -0500 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20200208161908.GN1663@brightrain.aerifal.cx> References: <20200207210331.GK1663@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: Rich Felker Subject: Re: [musl] fopen with "e" mode to close file descriptor in exec... functions On Sat, Feb 08, 2020 at 10:45:10AM +0300, Alexander Scherbatiy wrote: > Below are steps to reproduce it in docker, logs from docker and strace log. > > > docker run --rm -it alpine:3.11.3 ash > > apk add gcc > > apk add libc-dev > Copy the posix_spawn_sample.c code below (note it uses "ash" in 'char > *argv[] = {"ash", ,,,}' for posix_spawn on Alpine Linux ) > > > gcc -o posix_spawn_sample posix_spawn_sample.c > > ./posix_spawn_sample > > --- output --- > / # ./posix_spawn_sample > Child pid: 17 > PID=17 > 1 /bin/busybox /dev/pts/0 > 1 /bin/busybox /dev/pts/0 > 1 /bin/busybox /dev/pts/0 > 1 /bin/busybox /dev/tty > 16 /posix_spawn_sample /dev/pts/0 > 16 /posix_spawn_sample /dev/pts/0 > 16 /posix_spawn_sample /dev/pts/0 > 16 /posix_spawn_sample /test.log > ---------------- > > Note that "test.log" file is listed by "lsof -p PID" command. It's listed as being owned by pid 16, the parent, not pid 17, the child. That's expected. At first I didn't understand why lsof -p is showing these additional pids (parent and init) in addition to the requested one. But it seems since you're using Docker those are the *only* pids running, and you just hit the issue that busybox lsof does not support -p (or any options at all) and always lists all open files for all processes. It would be a lot better to have your test do like I suggested and ls -l /proc/$$/fd rather than running lsof. Then you will very clearly that the log file is not open. Or even run an interactive shell as the child so you can explore /proc yourself from it. Rich