From patchwork Wed Apr 20 18:51:41 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Hallyn X-Patchwork-Id: 11825 Received: (qmail 100707 invoked by alias); 20 Apr 2016 18:51:59 -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 99690 invoked by uid 89); 20 Apr 2016 18:51:57 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=0.8 required=5.0 tests=AWL, BAYES_50, KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2 spammy=*dev, st1, 1586, mydev X-HELO: youngberry.canonical.com Date: Wed, 20 Apr 2016 18:51:41 +0000 From: Serge Hallyn To: libc-alpha@sourceware.org Subject: Re: [PATCH] linux ttyname and ttyname_r: return link if appropriate Message-ID: <20160420185141.GA31095@ubuntumail> References: <20160415164652.GE8450@ubuntumail> <57111F9C.8030902@redhat.com> <20160415174245.GA9610@ubuntumail> <20160415184746.GA10830@ubuntumail> <20160415195938.GP6588@vapier.lan> <20160418195318.GB30476@ubuntumail> <20160418200222.GY5369@vapier.lan> <20160418202301.GA30919@ubuntumail> <20160420021012.GA19449@ubuntumail> <20160420022823.GT5369@vapier.lan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160420022823.GT5369@vapier.lan> User-Agent: Mutt/1.5.21 (2010-09-15) Quoting Mike Frysinger (vapier@gentoo.org): > On 20 Apr 2016 02:10, Serge Hallyn wrote: > > --- a/sysdeps/unix/sysv/linux/ttyname.c > > +++ b/sysdeps/unix/sysv/linux/ttyname.c > > > > + linux/Documentation/devices.txt */ > > should be a period at the end followed by two spaces > > > + int m = major (sb->st_rdev); > > you'll need to include sys/sysmacros.h in this file since you're using > major now. Hm, odd - it did build here fine. But presumably that's due to something in my local environment, so added it. New version below, thanks. > > + /* 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 */ > > should be "namespace. */" at the end ;) > > > --- a/sysdeps/unix/sysv/linux/ttyname_r.c > > +++ b/sysdeps/unix/sysv/linux/ttyname_r.c > > same comments here > -mike Subject: linux ttyname and ttyname_r: return link if appropriate 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 | 21 +++++++++++++++++++++ sysdeps/unix/sysv/linux/ttyname_r.c | 23 +++++++++++++++++++++++ 2 files changed, 44 insertions(+) diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c index 7a001b4..d0d8d2c 100644 --- a/sysdeps/unix/sysv/linux/ttyname.c +++ b/sysdeps/unix/sysv/linux/ttyname.c @@ -25,6 +25,7 @@ #include #include #include +#include #include <_itoa.h> @@ -33,6 +34,19 @@ 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 +184,19 @@ 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) + return strcpy (ttyname_buf, procname); } if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode)) diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c index d15bc74..d5f6f05 100644 --- a/sysdeps/unix/sysv/linux/ttyname_r.c +++ b/sysdeps/unix/sysv/linux/ttyname_r.c @@ -25,6 +25,7 @@ #include #include #include +#include #include <_itoa.h> @@ -32,6 +33,19 @@ static int getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino, int save, int *dostat) internal_function; +/* 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 int internal_function attribute_compat_text_section getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino, @@ -158,6 +172,15 @@ __ttyname_r (int fd, char *buf, size_t buflen) #endif ) return 0; + + /* 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 (buf, procname); + return 0; + } } /* Prepare the result buffer. */