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Linux: Require properly configured /dev/pts for PTYs

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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.zanella@linaro.org>
This commit is contained in:
Florian Weimer
2020-10-07 14:55:04 +02:00
parent 0f9793a556
commit 27fe5f2e67
6 changed files with 60 additions and 209 deletions
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73
sysdeps/unix/sysv/linux/grantpt.c
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@ -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 <zack@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 <sys/ioctl.h>
#include <termios.h>
#include <not-cancel.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);
}
/* 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. */
__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);
}
/* 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>