Package: libc6
Version: 2.31-13+deb11u3
Severity: normal
Tags: patch
X-Debbugs-Cc: iwien...@redhat.com

Dear Maintainer,

The glibc bug

 https://sourceware.org/bugzilla/show_bug.cgi?id=24941

fixed by

 
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=27fe5f2e67a0e4cc0526b1b32b55f8e519075edb

provides fixes for the grantpt() call deadlocking after fork().  This
seems rather esoteric, but has caused difficult to debug issues for
Ansible users, e.g.

 https://github.com/ansible/ansible/issues/59642

In opendev.org CI (zuul.opendev.org) several users hit this in various
ways as our execution environment is based on Debian Bullseye.  We
have pulled a more recent glibc into our images with

 https://review.opendev.org/c/zuul/zuul/+/849795

But hopefully we can find a solution that is helpful to everyone.

I have pulled the patch and applied it with minor fuzz updates against
2.31-13+deb11u3.  Could we consider having this applied?

Thanks,

-i

-- System Information:
Debian Release: 11.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 5.18.10-200.fc36.x86_64 (SMP w/12 CPU threads; PREEMPT)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: unable to detect

Versions of packages libc6 depends on:
ii  libcrypt1  1:4.4.18-4
ii  libgcc-s1  10.2.1-6

Versions of packages libc6 recommends:
ii  libidn2-0       2.3.0-5
pn  libnss-nis      <none>
pn  libnss-nisplus  <none>

Versions of packages libc6 suggests:
ii  debconf [debconf-2.0]  1.5.77
pn  glibc-doc              <none>
pn  libc-l10n              <none>
pn  locales                <none>

-- debconf information excluded
commit 27fe5f2e67a0e4cc0526b1b32b55f8e519075edb
Author: Florian Weimer <fwei...@redhat.com>
Date:   Wed Oct 7 14:55:04 2020 +0200

    Linux: Require properly configured /dev/pts for PTYs
    
    Current systems do not have BSD terminals, so the fallback code in
    posix_openpt/getpt does not do anything.  Also remove the file system
    check for /dev/pts.  Current systems always have a devpts file system
    mounted there if /dev/ptmx exists.
    
    grantpt is now essentially a no-op.  It only verifies that the
    argument is a ptmx-descriptor.  Therefore, this change indirectly
    addresses bug 24941.
    
    Reviewed-by: Adhemerval Zanella <adhemerval.zane...@linaro.org>
    (Cherry-picked by Ian Wienand <iwien...@redhat.com>)

Index: glibc-2.31/INSTALL
===================================================================
--- glibc-2.31.orig/INSTALL
+++ glibc-2.31/INSTALL
@@ -184,14 +184,9 @@ if 'CFLAGS' is specified it must enable
 '--enable-pt_chown'
      The file 'pt_chown' is a helper binary for 'grantpt' (*note
      Pseudo-Terminals: Allocation.) that is installed setuid root to fix
-     up pseudo-terminal ownership.  It is not built by default because
-     systems using the Linux kernel are commonly built with the 'devpts'
-     filesystem enabled and mounted at '/dev/pts', which manages
-     pseudo-terminal ownership automatically.  By using
-     '--enable-pt_chown', you may build 'pt_chown' and install it setuid
-     and owned by 'root'.  The use of 'pt_chown' introduces additional
-     security risks to the system and you should enable it only if you
-     understand and accept those risks.
+     up pseudo-terminal ownership on GNU/Hurd.  It is not required on
+     GNU/Linux, and the GNU C Library will not use the installed
+     'pt_chown' program when configured with '--enable-pt_chown'.
 
 '--disable-werror'
      By default, the GNU C Library is built with '-Werror'.  If you wish
Index: glibc-2.31/NEWS
===================================================================
--- glibc-2.31.orig/NEWS
+++ glibc-2.31/NEWS
@@ -399,6 +399,18 @@ Changes to build and runtime requirement
   Older GCC versions and non-GNU compilers are still supported when
   compiling programs that use the GNU C Library.
 
+* On Linux, the system administrator needs to configure /dev/pts with
+  the intended access modes for pseudo-terminals.  glibc no longer
+  attemps to adjust permissions of terminal devices.  The previous glibc
+  defaults ("tty" group, user read/write and group write) already
+  corresponded to what most systems used, so that grantpt did not
+  perform any adjustments.
+
+* On Linux, the posix_openpt and getpt functions no longer attempt to
+  use legacy (BSD) pseudo-terminals and assume that if /dev/ptmx exists
+  (and pseudo-terminals are supported), a devpts file system is mounted
+  on /dev/pts.  Current systems already meet these requirements.
+
 Security related changes:
 
   CVE-2019-7309: x86-64 memcmp used signed Jcc instructions to check
Index: glibc-2.31/sysdeps/unix/sysv/linux/getpt.c
===================================================================
--- glibc-2.31.orig/sysdeps/unix/sysv/linux/getpt.c
+++ glibc-2.31/sysdeps/unix/sysv/linux/getpt.c
@@ -16,69 +16,18 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <fcntl.h>
-#include <stdlib.h>
 #include <unistd.h>
 #include <paths.h>
-#include <sys/statfs.h>
-
-#include "linux_fsinfo.h"
 
 /* Path to the master pseudo terminal cloning device.  */
 #define _PATH_DEVPTMX _PATH_DEV "ptmx"
-/* Directory containing the UNIX98 pseudo terminals.  */
-#define _PATH_DEVPTS _PATH_DEV "pts"
-
-/* Prototype for function that opens BSD-style master pseudo-terminals.  */
-extern int __bsd_openpt (int oflag) attribute_hidden;
 
 /* Open a master pseudo terminal and return its file descriptor.  */
 int
 __posix_openpt (int oflag)
 {
-  static int have_no_dev_ptmx;
-  int fd;
-
-  if (!have_no_dev_ptmx)
-    {
-      fd = __open (_PATH_DEVPTMX, oflag);
-      if (fd != -1)
-       {
-         struct statfs fsbuf;
-         static int devpts_mounted;
-
-         /* Check that the /dev/pts filesystem is mounted
-            or if /dev is a devfs filesystem (this implies /dev/pts).  */
-         if (devpts_mounted
-             || (__statfs (_PATH_DEVPTS, &fsbuf) == 0
-                 && fsbuf.f_type == DEVPTS_SUPER_MAGIC)
-             || (__statfs (_PATH_DEV, &fsbuf) == 0
-                 && fsbuf.f_type == DEVFS_SUPER_MAGIC))
-           {
-             /* Everything is ok.  */
-             devpts_mounted = 1;
-             return fd;
-           }
-
-         /* If /dev/pts is not mounted then the UNIX98 pseudo terminals
-            are not usable.  */
-         __close (fd);
-         have_no_dev_ptmx = 1;
-         __set_errno (ENOENT);
-       }
-      else
-       {
-         if (errno == ENOENT || errno == ENODEV)
-           have_no_dev_ptmx = 1;
-         else
-           return -1;
-       }
-    }
-  else
-    __set_errno (ENOENT);
-
-  return -1;
+  return __open (_PATH_DEVPTMX, oflag);
 }
 weak_alias (__posix_openpt, posix_openpt)
 
@@ -86,17 +35,6 @@ weak_alias (__posix_openpt, posix_openpt
 int
 __getpt (void)
 {
-  int fd = __posix_openpt (O_RDWR);
-  if (fd == -1)
-    fd = __bsd_openpt (O_RDWR);
-  return fd;
+  return __posix_openpt (O_RDWR);
 }
 weak_alias (__getpt, getpt)
-
-
-#define PTYNAME1 "pqrstuvwxyzabcde";
-#define PTYNAME2 "0123456789abcdef";
-
-#define HAVE_GETPT
-#define HAVE_POSIX_OPENPT
-#include <sysdeps/unix/bsd/getpt.c>
Index: glibc-2.31/sysdeps/unix/sysv/linux/grantpt.c
===================================================================
--- glibc-2.31.orig/sysdeps/unix/sysv/linux/grantpt.c
+++ glibc-2.31/sysdeps/unix/sysv/linux/grantpt.c
@@ -1,44 +1,41 @@
-#include <assert.h>
-#include <ctype.h>
-#include <dirent.h>
+/* grantpt implementation for Linux.
+   Copyright (C) 1998-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Zack Weinberg <z...@rabi.phys.columbia.edu>, 1998.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
 #include <errno.h>
-#include <fcntl.h>
-#include <paths.h>
 #include <stdlib.h>
-#include <unistd.h>
-
-#include <not-cancel.h>
+#include <sys/ioctl.h>
+#include <termios.h>
 
-#include "pty-private.h"
-
-#if HAVE_PT_CHOWN
-/* Close all file descriptors except the one specified.  */
-static void
-close_all_fds (void)
+int
+grantpt (int fd)
 {
-  DIR *dir = __opendir ("/proc/self/fd");
-  if (dir != NULL)
-    {
-      struct dirent64 *d;
-      while ((d = __readdir64 (dir)) != NULL)
-       if (isdigit (d->d_name[0]))
-         {
-           char *endp;
-           long int fd = strtol (d->d_name, &endp, 10);
-           if (*endp == '\0' && fd != PTY_FILENO && fd != dirfd (dir))
-             __close_nocancel_nostatus (fd);
-         }
-
-      __closedir (dir);
-
-      int nullfd = __open_nocancel (_PATH_DEVNULL, O_RDONLY);
-      assert (nullfd == STDIN_FILENO);
-      nullfd = __open_nocancel (_PATH_DEVNULL, O_WRONLY);
-      assert (nullfd == STDOUT_FILENO);
-      __dup2 (STDOUT_FILENO, STDERR_FILENO);
-    }
+  /* Without pt_chown on Linux, we have delegated the creation of the
+     pty node with the right group and permission mode to the kernel, and
+     non-root users are unlikely to be able to change it. Therefore let's
+     consider that POSIX enforcement is the responsibility of the whole
+     system and not only the GNU libc.   */
+
+  /* Verify that fd refers to a ptmx descriptor.  */
+  unsigned int ptyno;
+  int ret = __ioctl (fd, TIOCGPTN, &ptyno);
+  if (ret != 0 && errno == ENOTTY)
+    /* POSIX requires EINVAL instead of ENOTTY provided by the kernel.  */
+    __set_errno (EINVAL);
+  return ret;
 }
-# define CLOSE_ALL_FDS() close_all_fds()
-#endif
-
-#include <sysdeps/unix/grantpt.c>
Index: glibc-2.31/sysdeps/unix/sysv/linux/ptsname.c
===================================================================
--- glibc-2.31.orig/sysdeps/unix/sysv/linux/ptsname.c
+++ glibc-2.31/sysdeps/unix/sysv/linux/ptsname.c
@@ -21,39 +21,14 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
-#include <sys/stat.h>
-#include <sys/sysmacros.h>
 #include <termios.h>
 #include <unistd.h>
 
 #include <_itoa.h>
 
-/* Check if DEV corresponds to a master pseudo terminal device.  */
-#define MASTER_P(Dev)                                                  \
-  (__gnu_dev_major ((Dev)) == 2                                                
\
-   || (__gnu_dev_major ((Dev)) == 4                                    \
-       && __gnu_dev_minor ((Dev)) >= 128 && __gnu_dev_minor ((Dev)) < 192) \
-   || (__gnu_dev_major ((Dev)) >= 128 && __gnu_dev_major ((Dev)) < 136))
-
-/* Check if DEV corresponds to a slave pseudo terminal device.  */
-#define SLAVE_P(Dev)                                                   \
-  (__gnu_dev_major ((Dev)) == 3                                                
\
-   || (__gnu_dev_major ((Dev)) == 4                                    \
-       && __gnu_dev_minor ((Dev)) >= 192 && __gnu_dev_minor ((Dev)) < 256) \
-   || (__gnu_dev_major ((Dev)) >= 136 && __gnu_dev_major ((Dev)) < 144))
-
-/* Note that major number 4 corresponds to the old BSD style pseudo
-   terminal devices.  As of Linux 2.1.115 these are no longer
-   supported.  They have been replaced by major numbers 2 (masters)
-   and 3 (slaves).  */
-
 /* Directory where we can find the slave pty nodes.  */
 #define _PATH_DEVPTS "/dev/pts/"
 
-/* The are declared in getpt.c.  */
-extern const char __libc_ptyname1[] attribute_hidden;
-extern const char __libc_ptyname2[] attribute_hidden;
-
 /* Static buffer for `ptsname'.  */
 static char buffer[sizeof (_PATH_DEVPTS) + 20];
 
@@ -68,19 +43,15 @@ ptsname (int fd)
 }
 
 
+/* Store at most BUFLEN characters of the pathname of the slave pseudo
+   terminal associated with the master FD is open on in BUF.
+   Return 0 on success, otherwise an error number.  */
 int
-__ptsname_internal (int fd, char *buf, size_t buflen, struct stat64 *stp)
+__ptsname_r (int fd, char *buf, size_t buflen)
 {
   int save_errno = errno;
   unsigned int ptyno;
 
-  if (!__isatty (fd))
-    {
-      __set_errno (ENOTTY);
-      return ENOTTY;
-    }
-
-#ifdef TIOCGPTN
   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
     {
       /* Buffer we use to print the number in.  For a maximum size for
@@ -101,67 +72,11 @@ __ptsname_internal (int fd, char *buf, s
 
       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
     }
-  else if (errno != EINVAL)
-    return errno;
   else
-#endif
-    {
-      char *p;
-
-      if (buflen < strlen (_PATH_TTY) + 3)
-       {
-         __set_errno (ERANGE);
-         return ERANGE;
-       }
-
-      if (__fxstat64 (_STAT_VER, fd, stp) < 0)
-       return errno;
-
-      /* Check if FD really is a master pseudo terminal.  */
-      if (! MASTER_P (stp->st_rdev))
-       {
-         __set_errno (ENOTTY);
-         return ENOTTY;
-       }
-
-      ptyno = __gnu_dev_minor (stp->st_rdev);
-
-      if (ptyno / 16 >= strlen (__libc_ptyname1))
-       {
-         __set_errno (ENOTTY);
-         return ENOTTY;
-       }
-
-      p = __stpcpy (buf, _PATH_TTY);
-      p[0] = __libc_ptyname1[ptyno / 16];
-      p[1] = __libc_ptyname2[ptyno % 16];
-      p[2] = '\0';
-    }
-
-  if (__xstat64 (_STAT_VER, buf, stp) < 0)
+    /* Bad file descriptor, or not a ptmx descriptor.  */
     return errno;
 
-  /* Check if the name we're about to return really corresponds to a
-     slave pseudo terminal.  */
-  if (! S_ISCHR (stp->st_mode) || ! SLAVE_P (stp->st_rdev))
-    {
-      /* This really is a configuration problem.  */
-      __set_errno (ENOTTY);
-      return ENOTTY;
-    }
-
   __set_errno (save_errno);
   return 0;
 }
-
-
-/* Store at most BUFLEN characters of the pathname of the slave pseudo
-   terminal associated with the master FD is open on in BUF.
-   Return 0 on success, otherwise an error number.  */
-int
-__ptsname_r (int fd, char *buf, size_t buflen)
-{
-  struct stat64 st;
-  return __ptsname_internal (fd, buf, buflen, &st);
-}
 weak_alias (__ptsname_r, ptsname_r)

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