From patchwork Mon Apr 18 19:53:18 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Hallyn X-Patchwork-Id: 11792 Received: (qmail 66942 invoked by alias); 18 Apr 2016 19:53:35 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 66881 invoked by uid 89); 18 Apr 2016 19:53:35 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.6 required=5.0 tests=AWL, BAYES_00, KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2 spammy=UD:st_mode, strcpy, H*Ad:D*ubuntu.com, our X-HELO: youngberry.canonical.com Date: Mon, 18 Apr 2016 19:53:18 +0000 From: Serge Hallyn To: libc-alpha@sourceware.org, Serge Hallyn Subject: [PATCH 1/2] linux ttyname: return link if appropriate Message-ID: <20160418195318.GB30476@ubuntumail> References: <20160415152929.GA7932@ubuntumail> <5711165D.5040902@redhat.com> <20160415164652.GE8450@ubuntumail> <57111F9C.8030902@redhat.com> <20160415174245.GA9610@ubuntumail> <20160415184746.GA10830@ubuntumail> <20160415195938.GP6588@vapier.lan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160415195938.GP6588@vapier.lan> User-Agent: Mutt/1.5.21 (2010-09-15) The current ttyname does the wrong thing in two cases: 1. If the passed-in link (say /proc/self/fd/0) points to a device, say /dev/pts/2, in a parent mount namespace, and a /dev/pts/2 exists (in a different devpts) in the current namespace, then it returns /dev/pts/2. But /dev/pts/2 is NOT the current tty, it is a different file and device. 2. If the passed-in link (say /proc/self/fd/0) points to a device, say /dev/pts/2, in a parent mount namespace, and /dev/pts/2 does not exist in the current namespace, it returns success but an empty name. As far as I can tell, there is no reason for it to not return /proc/self/fd/0. http://pubs.opengroup.org/onlinepubs/009695399/functions/ttyname.html does not say anything about not returning a link. --- sysdeps/unix/sysv/linux/ttyname.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c index 7a001b4..430fb48 100644 --- a/sysdeps/unix/sysv/linux/ttyname.c +++ b/sysdeps/unix/sysv/linux/ttyname.c @@ -33,6 +33,19 @@ char *__ttyname; #endif +/* Return true if this is a UNIX98 pty device, as defined in + linux/Documentation/devices.txt */ +static int +is_pty (struct stat64 *sb) +{ +#ifdef _STATBUF_ST_RDEV + int m = major (sb->st_rdev); + return (136 <= m && m <= 143); +#else + return false; +#endif +} + static char *getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat) internal_function; @@ -170,12 +183,22 @@ ttyname (int fd) #ifdef _STATBUF_ST_RDEV && S_ISCHR (st1.st_mode) && st1.st_rdev == st.st_rdev + && st1.st_dev == st.st_dev #else && st1.st_ino == st.st_ino && st1.st_dev == st.st_dev #endif ) return ttyname_buf; + + /* If the link doesn't exist, then it points to a device in another + namespace. If it is a UNIX98 pty, then return the /proc/self + fd, as it points to a name unreachable in our namespace */ + if (is_pty (&st) && strlen (procname) < buflen - 1) + { + strcpy (ttyname_buf, procname); + return ttyname_buf; + } } if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))