261 lines
6.6 KiB
C
261 lines
6.6 KiB
C
/* Copyright (C) 1998-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <grp.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/resource.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "pty-private.h"
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/* Return the result of ptsname_r in the buffer pointed to by PTS,
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which should be of length BUF_LEN. If it is too long to fit in
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this buffer, a sufficiently long buffer is allocated using malloc,
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and returned in PTS. 0 is returned upon success, -1 otherwise. */
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static int
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pts_name (int fd, char **pts, size_t buf_len, struct stat64 *stp)
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{
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int rv;
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char *buf = *pts;
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for (;;)
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{
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char *new_buf;
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if (buf_len)
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{
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rv = __ptsname_internal (fd, buf, buf_len, stp);
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if (rv != 0)
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{
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if (rv == ENOTTY)
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/* ptsname_r returns with ENOTTY to indicate
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a descriptor not referring to a pty master.
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For this condition, grantpt must return EINVAL. */
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rv = EINVAL;
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errno = rv; /* Not necessarily set by __ptsname_r. */
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break;
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}
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if (memchr (buf, '\0', buf_len))
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/* We succeeded and the returned name fit in the buffer. */
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break;
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/* Try again with a longer buffer. */
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buf_len += buf_len; /* Double it */
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}
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else
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/* No initial buffer; start out by mallocing one. */
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buf_len = 128; /* First time guess. */
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if (buf != *pts)
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/* We've already malloced another buffer at least once. */
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new_buf = (char *) realloc (buf, buf_len);
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else
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new_buf = (char *) malloc (buf_len);
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if (! new_buf)
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{
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rv = -1;
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__set_errno (ENOMEM);
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break;
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}
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buf = new_buf;
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}
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if (rv == 0)
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*pts = buf; /* Return buffer to the user. */
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else if (buf != *pts)
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free (buf); /* Free what we malloced when returning an error. */
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return rv;
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}
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/* Change the ownership and access permission of the slave pseudo
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terminal associated with the master pseudo terminal specified
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by FD. */
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int
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grantpt (int fd)
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{
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int retval = -1;
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#ifdef PATH_MAX
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char _buf[PATH_MAX];
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#else
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char _buf[512];
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#endif
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char *buf = _buf;
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struct stat64 st;
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if (__glibc_unlikely (pts_name (fd, &buf, sizeof (_buf), &st)))
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{
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int save_errno = errno;
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/* Check, if the file descriptor is valid. pts_name returns the
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wrong errno number, so we cannot use that. */
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if (__libc_fcntl (fd, F_GETFD) == -1 && errno == EBADF)
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return -1;
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/* If the filedescriptor is no TTY, grantpt has to set errno
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to EINVAL. */
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if (save_errno == ENOTTY)
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__set_errno (EINVAL);
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else
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__set_errno (save_errno);
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return -1;
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}
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/* Make sure that we own the device. */
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uid_t uid = __getuid ();
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if (st.st_uid != uid)
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{
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if (__chown (buf, uid, st.st_gid) < 0)
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goto helper;
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}
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static int tty_gid = -1;
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if (__glibc_unlikely (tty_gid == -1))
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{
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char *grtmpbuf;
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struct group grbuf;
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size_t grbuflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
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struct group *p;
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/* Get the group ID of the special `tty' group. */
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if (grbuflen == (size_t) -1L)
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/* `sysconf' does not support _SC_GETGR_R_SIZE_MAX.
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Try a moderate value. */
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grbuflen = 1024;
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grtmpbuf = (char *) __alloca (grbuflen);
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__getgrnam_r (TTY_GROUP, &grbuf, grtmpbuf, grbuflen, &p);
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if (p != NULL)
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tty_gid = p->gr_gid;
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}
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gid_t gid = tty_gid == -1 ? __getgid () : tty_gid;
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#if HAVE_PT_CHOWN
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/* Make sure the group of the device is that special group. */
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if (st.st_gid != gid)
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{
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if (__chown (buf, uid, gid) < 0)
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goto helper;
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}
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/* Make sure the permission mode is set to readable and writable by
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the owner, and writable by the group. */
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mode_t mode = S_IRUSR|S_IWUSR|S_IWGRP;
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#else
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/* When built without pt_chown, we have delegated the creation of the
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pty node with the right group and permission mode to the kernel, and
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non-root users are unlikely to be able to change it. Therefore let's
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consider that POSIX enforcement is the responsibility of the whole
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system and not only the GNU libc. Thus accept different group or
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permission mode. */
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/* Make sure the permission is set to readable and writable by the
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owner. For security reasons, make it writable by the group only
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when originally writable and when the group of the device is that
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special group. */
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mode_t mode = S_IRUSR|S_IWUSR
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|((st.st_gid == gid) ? (st.st_mode & S_IWGRP) : 0);
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#endif
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if ((st.st_mode & ACCESSPERMS) != mode)
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{
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if (__chmod (buf, mode) < 0)
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goto helper;
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}
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retval = 0;
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goto cleanup;
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/* We have to use the helper program if it is available. */
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helper:;
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#if HAVE_PT_CHOWN
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pid_t pid = __fork ();
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if (pid == -1)
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goto cleanup;
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else if (pid == 0)
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{
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/* Disable core dumps. */
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struct rlimit rl = { 0, 0 };
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__setrlimit (RLIMIT_CORE, &rl);
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/* We pass the master pseudo terminal as file descriptor PTY_FILENO. */
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if (fd != PTY_FILENO)
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if (__dup2 (fd, PTY_FILENO) < 0)
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_exit (FAIL_EBADF);
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# ifdef CLOSE_ALL_FDS
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CLOSE_ALL_FDS ();
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# endif
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execle (_PATH_PT_CHOWN, __basename (_PATH_PT_CHOWN), NULL, NULL);
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_exit (FAIL_EXEC);
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}
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else
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{
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int w;
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if (__waitpid (pid, &w, 0) == -1)
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goto cleanup;
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if (!WIFEXITED (w))
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__set_errno (ENOEXEC);
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else
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switch (WEXITSTATUS (w))
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{
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case 0:
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retval = 0;
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break;
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case FAIL_EBADF:
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__set_errno (EBADF);
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break;
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case FAIL_EINVAL:
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__set_errno (EINVAL);
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break;
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case FAIL_EACCES:
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__set_errno (EACCES);
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break;
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case FAIL_EXEC:
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__set_errno (ENOEXEC);
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break;
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case FAIL_ENOMEM:
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__set_errno (ENOMEM);
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break;
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default:
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assert(! "grantpt: internal error: invalid exit code from pt_chown");
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}
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}
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#endif
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cleanup:
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if (buf != _buf)
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free (buf);
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return retval;
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}
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libc_hidden_def (grantpt)
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