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-rw-r--r--conf/mtab/mtab_linux.c565
1 files changed, 565 insertions, 0 deletions
diff --git a/conf/mtab/mtab_linux.c b/conf/mtab/mtab_linux.c
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+++ b/conf/mtab/mtab_linux.c
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+/*
+ * Copyright (c) 1997-2014 Erez Zadok
+ * Copyright (c) 1990 Jan-Simon Pendry
+ * Copyright (c) 1990 Imperial College of Science, Technology & Medicine
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Jan-Simon Pendry at Imperial College, London.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *
+ * File: am-utils/conf/mtab/mtab_linux.c
+ *
+ */
+
+/* This file was adapted by Red Hat for Linux from mtab_file.c */
+
+/*
+ * The locking code must be kept in sync with that used
+ * by the mount command in util-linux, otherwise you'll
+ * end with with race conditions leading to a corrupt
+ * /etc/mtab, particularly when AutoFS is used on same
+ * machine as AMD.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif /* HAVE_CONFIG_H */
+#include <am_defs.h>
+#include <amu.h>
+
+#define NFILE_RETRIES 10 /* number of retries (seconds) */
+#define LOCK_TIMEOUT 10
+
+#ifdef MOUNT_TABLE_ON_FILE
+
+# define PROC_MOUNTS "/proc/mounts"
+
+static FILE *mnt_file = NULL;
+/* Information about mtab. ------------------------------------*/
+static int have_mtab_info = 0;
+static int var_mtab_does_not_exist = 0;
+static int var_mtab_is_a_symlink = 0;
+/* Flag for already existing lock file. */
+static int we_created_lockfile = 0;
+static int lockfile_fd = -1;
+
+
+static void
+get_mtab_info(void)
+{
+ struct stat mtab_stat;
+
+ if (!have_mtab_info) {
+ if (lstat(MOUNTED, &mtab_stat))
+ var_mtab_does_not_exist = 1;
+ else if (S_ISLNK(mtab_stat.st_mode))
+ var_mtab_is_a_symlink = 1;
+ have_mtab_info = 1;
+ }
+}
+
+
+static int
+mtab_is_a_symlink(void)
+{
+ get_mtab_info();
+ return var_mtab_is_a_symlink;
+}
+
+
+static int
+mtab_is_writable()
+{
+ static int ret = -1;
+
+ /*
+ * Should we write to /etc/mtab upon an update? Probably not if it is a
+ * symlink to /proc/mounts, since that would create a file /proc/mounts in
+ * case the proc filesystem is not mounted.
+ */
+ if (mtab_is_a_symlink())
+ return 0;
+
+ if (ret == -1) {
+ int fd = open(MOUNTED, O_RDWR | O_CREAT, 0644);
+ if (fd >= 0) {
+ close(fd);
+ ret = 1;
+ } else
+ ret = 0;
+ }
+ return ret;
+}
+
+
+static void
+setlkw_timeout(int sig)
+{
+ /* nothing, fcntl will fail anyway */
+}
+
+
+/*
+ * Create the lock file.
+ * The lock file will be removed if we catch a signal or when we exit.
+ *
+ * The old code here used flock on a lock file /etc/mtab~ and deleted
+ * this lock file afterwards. However, as rgooch remarks, that has a
+ * race: a second mount may be waiting on the lock and proceed as
+ * soon as the lock file is deleted by the first mount, and immediately
+ * afterwards a third mount comes, creates a new /etc/mtab~, applies
+ * flock to that, and also proceeds, so that the second and third mount
+ * now both are scribbling in /etc/mtab.
+ * The new code uses a link() instead of a creat(), where we proceed
+ * only if it was us that created the lock, and hence we always have
+ * to delete the lock afterwards. Now the use of flock() is in principle
+ * superfluous, but avoids an arbitrary sleep().
+ */
+
+/*
+ * Where does the link point to? Obvious choices are mtab and mtab~~.
+ * HJLu points out that the latter leads to races. Right now we use
+ * mtab~.<pid> instead.
+ */
+#define MOUNTED_LOCK "/etc/mtab~"
+#define MOUNTLOCK_LINKTARGET MOUNTED_LOCK "%d"
+
+int
+lock_mtab(void)
+{
+ int tries = 100000, i;
+ char *linktargetfile;
+ size_t l;
+ int rc = 1;
+
+ /*
+ * Redhat's original code set a signal handler called "handler()" for all
+ * non-ALRM signals. The handler called unlock_mntlist(), plog'ed the
+ * signal name, and then exit(1)! Never, ever, exit() from inside a
+ * utility function. This messed up Amd's careful signal-handling code,
+ * and caused Amd to abort uncleanly only any other "innocent" signal
+ * (even simple SIGUSR1), leaving behind a hung Amd mnt point. That code
+ * should have at least restored the signal handlers' states upon a
+ * successful mtab unlocking. Anyway, that handler was unnecessary,
+ * because will call unlock_mntlist() properly anyway on exit.
+ */
+ setup_sighandler(SIGALRM, setlkw_timeout);
+
+ /* somewhat clumsy, but some ancient systems do not have snprintf() */
+ /* use 20 as upper bound for the length of %d output */
+ l = strlen(MOUNTLOCK_LINKTARGET) + 20;
+ linktargetfile = xmalloc(l);
+ xsnprintf(linktargetfile, l, MOUNTLOCK_LINKTARGET, getpid());
+
+ i = open(linktargetfile, O_WRONLY|O_CREAT, 0);
+ if (i < 0) {
+ int errsv = errno;
+ /*
+ * linktargetfile does not exist (as a file) and we cannot create
+ * it. Read-only filesystem? Too many files open in the system?
+ * Filesystem full?
+ */
+ plog(XLOG_ERROR, "%s: can't create lock file %s: %s "
+ "(use -n flag to override)", __func__,
+ linktargetfile, strerror(errsv));
+ goto error;
+ }
+ close(i);
+
+
+ /* Repeat until it was us who made the link */
+ while (!we_created_lockfile) {
+ struct flock flock;
+ int errsv, j;
+
+ j = link(linktargetfile, MOUNTED_LOCK);
+ errsv = errno;
+
+ if (j < 0 && errsv != EEXIST) {
+ (void) unlink(linktargetfile);
+ plog(XLOG_ERROR, "can't link lock file %s: %s ",
+ MOUNTED_LOCK, strerror(errsv));
+ rc = 0;
+ goto error;
+ }
+
+ lockfile_fd = open(MOUNTED_LOCK, O_WRONLY);
+ if (lockfile_fd < 0) {
+ int errsv = errno;
+ /* Strange... Maybe the file was just deleted? */
+ if (errno == ENOENT && tries-- > 0) {
+ if (tries % 200 == 0)
+ usleep(30);
+ continue;
+ }
+ (void) unlink(linktargetfile);
+ plog(XLOG_ERROR,"%s: can't open lock file %s: %s ", __func__,
+ MOUNTED_LOCK, strerror(errsv));
+ rc = 0;
+ goto error;
+ }
+
+ flock.l_type = F_WRLCK;
+ flock.l_whence = SEEK_SET;
+ flock.l_start = 0;
+ flock.l_len = 0;
+
+ if (j == 0) {
+ /* We made the link. Now claim the lock. */
+ if (fcntl(lockfile_fd, F_SETLK, &flock) == -1) {
+ int errsv = errno;
+ plog(XLOG_ERROR, "%s: Can't lock lock file %s: %s", __func__,
+ MOUNTED_LOCK, strerror(errsv));
+ /* proceed, since it was us who created the lockfile anyway */
+ }
+ we_created_lockfile = 1;
+ (void) unlink(linktargetfile);
+ } else {
+ static int tries = 0;
+
+ /* Someone else made the link. Wait. */
+ alarm(LOCK_TIMEOUT);
+
+ if (fcntl(lockfile_fd, F_SETLKW, &flock) == -1) {
+ int errsv = errno;
+ (void) unlink(linktargetfile);
+ plog(XLOG_ERROR, "%s: can't lock lock file %s: %s", __func__,
+ MOUNTED_LOCK, (errno == EINTR) ?
+ "timed out" : strerror(errsv));
+ rc = 0;
+ goto error;
+ }
+ alarm(0);
+ /*
+ * Limit the number of iterations - maybe there
+ * still is some old /etc/mtab~
+ */
+ ++tries;
+ if (tries % 200 == 0)
+ usleep(30);
+ if (tries > 100000) {
+ (void) unlink(linktargetfile);
+ close(lockfile_fd);
+ plog(XLOG_ERROR,
+ "%s: Cannot create link %s; Perhaps there is a stale lock file?",
+ __func__, MOUNTED_LOCK);
+ rc = 0;
+ goto error;
+ }
+ close(lockfile_fd);
+ }
+ }
+
+error:
+ XFREE(linktargetfile);
+
+ return rc;
+}
+
+
+static FILE *
+open_locked_mtab(const char *mnttabname, char *mode, char *fs)
+{
+ FILE *mfp = NULL;
+
+ if (mnt_file) {
+ dlog("Forced close on %s in read_mtab", mnttabname);
+ endmntent(mnt_file);
+ mnt_file = NULL;
+ }
+
+ if (!mtab_is_a_symlink() &&
+ !lock_mtab()) {
+ plog(XLOG_ERROR, "%s: Couldn't lock mtab", __func__);
+ return 0;
+ }
+
+ mfp = setmntent((char *)mnttabname, mode);
+ if (!mfp) {
+ plog(XLOG_ERROR, "%s: setmntent(\"%s\", \"%s\"): %m", __func__, mnttabname,
+ mode);
+ return 0;
+ }
+ return mfp;
+}
+
+
+/*
+ * Unlock the mount table
+ */
+void
+unlock_mntlist(void)
+{
+ if (mnt_file || we_created_lockfile)
+ dlog("unlock_mntlist: releasing");
+ if (mnt_file) {
+ endmntent(mnt_file);
+ mnt_file = NULL;
+ }
+ if (we_created_lockfile) {
+ close(lockfile_fd);
+ lockfile_fd = -1;
+ unlink(MOUNTED_LOCK);
+ we_created_lockfile = 0;
+ }
+}
+
+
+/*
+ * Write out a mount list
+ */
+void
+rewrite_mtab(mntlist *mp, const char *mnttabname)
+{
+ FILE *mfp;
+ int error = 0;
+ char tmpname[64];
+ int retries;
+ int tmpfd;
+ char *cp;
+ char mcp[128];
+
+ if (!mtab_is_writable()) {
+ return;
+ }
+
+ /*
+ * Concoct a temporary name in the same directory as the target mount
+ * table so that rename() will work.
+ */
+ xstrlcpy(mcp, mnttabname, sizeof(mcp));
+ cp = strrchr(mcp, '/');
+ if (cp) {
+ memmove(tmpname, mcp, cp - mcp);
+ tmpname[cp - mcp] = '\0';
+ } else {
+ plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mnttabname);
+ tmpname[0] = '.';
+ tmpname[1] = '\0';
+ }
+ xstrlcat(tmpname, "/mtabXXXXXX", sizeof(tmpname));
+ retries = 0;
+ enfile1:
+#ifdef HAVE_MKSTEMP
+ tmpfd = mkstemp(tmpname);
+ fchmod(tmpfd, 0644);
+#else /* not HAVE_MKSTEMP */
+ mktemp(tmpname);
+ tmpfd = open(tmpname, O_RDWR | O_CREAT | O_TRUNC, 0644);
+#endif /* not HAVE_MKSTEMP */
+ if (tmpfd < 0) {
+ if (errno == ENFILE && retries++ < NFILE_RETRIES) {
+ sleep(1);
+ goto enfile1;
+ }
+ plog(XLOG_ERROR, "%s: open: %m", tmpname);
+ return;
+ }
+ if (close(tmpfd) < 0)
+ plog(XLOG_ERROR, "%s: Couldn't close tmp file descriptor: %m", __func__);
+
+ retries = 0;
+ enfile2:
+ mfp = setmntent(tmpname, "w");
+ if (!mfp) {
+ if (errno == ENFILE && retries++ < NFILE_RETRIES) {
+ sleep(1);
+ goto enfile2;
+ }
+ plog(XLOG_ERROR, "%s: setmntent(\"%s\", \"w\"): %m", __func__, tmpname);
+ error = 1;
+ goto out;
+ }
+ while (mp) {
+ if (mp->mnt) {
+ if (addmntent(mfp, mp->mnt)) {
+ plog(XLOG_ERROR, "%s: Can't write entry to %s", __func__, tmpname);
+ error = 1;
+ goto out;
+ }
+ }
+ mp = mp->mnext;
+ }
+
+ /*
+ * SunOS 4.1 manuals say that the return code from entmntent()
+ * is always 1 and to treat as a void. That means we need to
+ * call fflush() to make sure the new mtab file got written.
+ */
+ if (fflush(mfp)) {
+ plog(XLOG_ERROR, "flush new mtab file: %m");
+ error = 1;
+ goto out;
+ }
+ (void) endmntent(mfp);
+
+ /*
+ * Rename temporary mtab to real mtab
+ */
+ if (rename(tmpname, mnttabname) < 0) {
+ plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mnttabname);
+ error = 1;
+ goto out;
+ }
+ out:
+ if (error)
+ (void) unlink(tmpname);
+}
+
+
+static void
+mtab_stripnl(char *s)
+{
+ do {
+ s = strchr(s, '\n');
+ if (s)
+ *s++ = ' ';
+ } while (s);
+}
+
+
+/*
+ * Append a mntent structure to the
+ * current mount table.
+ */
+void
+write_mntent(mntent_t *mp, const char *mnttabname)
+{
+ int retries = 0;
+ FILE *mfp;
+
+ if (!mtab_is_writable()) {
+ return;
+ }
+
+ enfile:
+ mfp = open_locked_mtab(mnttabname, "a", mp->mnt_dir);
+ if (mfp) {
+ mtab_stripnl(mp->mnt_opts);
+ if (addmntent(mfp, mp))
+ plog(XLOG_ERROR, "%s: Couldn't write %s: %m", __func__, mnttabname);
+ if (fflush(mfp))
+ plog(XLOG_ERROR, "%s: Couldn't flush %s: %m", __func__, mnttabname);
+ (void) endmntent(mfp);
+ } else {
+ if (errno == ENFILE && retries < NFILE_RETRIES) {
+ sleep(1);
+ goto enfile;
+ }
+ plog(XLOG_ERROR, "%s: setmntent(\"%s\", \"a\"): %m", __func__, mnttabname);
+ }
+
+ unlock_mntlist();
+}
+
+#endif /* MOUNT_TABLE_ON_FILE */
+
+
+static mntent_t *
+mnt_dup(mntent_t *mp)
+{
+ mntent_t *new_mp = ALLOC(mntent_t);
+
+ new_mp->mnt_fsname = xstrdup(mp->mnt_fsname);
+ new_mp->mnt_dir = xstrdup(mp->mnt_dir);
+ new_mp->mnt_type = xstrdup(mp->mnt_type);
+ new_mp->mnt_opts = xstrdup(mp->mnt_opts);
+
+ new_mp->mnt_freq = mp->mnt_freq;
+ new_mp->mnt_passno = mp->mnt_passno;
+
+#ifdef HAVE_MNTENT_T_MNT_TIME
+# ifdef HAVE_MNTENT_T_MNT_TIME_STRING
+ new_mp->mnt_time = xstrdup(mp->mnt_time);
+# else /* not HAVE_MNTENT_T_MNT_TIME_STRING */
+ new_mp->mnt_time = mp->mnt_time;
+# endif /* not HAVE_MNTENT_T_MNT_TIME_STRING */
+#endif /* HAVE_MNTENT_T_MNT_TIME */
+
+#ifdef HAVE_MNTENT_T_MNT_CNODE
+ new_mp->mnt_cnode = mp->mnt_cnode;
+#endif /* HAVE_MNTENT_T_MNT_CNODE */
+
+ return new_mp;
+}
+
+
+/*
+ * Read a mount table into memory
+ */
+mntlist *
+read_mtab(char *fs, const char *mnttabname)
+{
+ mntlist **mpp, *mhp;
+
+ mntent_t *mep;
+
+ FILE *mfp = open_locked_mtab(mnttabname, "r+", fs);
+
+ if (!mfp)
+ return 0;
+
+ mpp = &mhp;
+
+ /*
+ * XXX - In SunOS 4 there is (yet another) memory leak
+ * which loses 1K the first time getmntent is called.
+ * (jsp)
+ */
+ while ((mep = getmntent(mfp))) {
+ /*
+ * Allocate a new slot
+ */
+ *mpp = ALLOC(struct mntlist);
+
+ /*
+ * Copy the data returned by getmntent
+ */
+ (*mpp)->mnt = mnt_dup(mep);
+
+ /*
+ * Move to next pointer
+ */
+ mpp = &(*mpp)->mnext;
+ }
+ *mpp = NULL;
+
+#ifdef MOUNT_TABLE_ON_FILE
+ /*
+ * If we are not updating the mount table then we
+ * can free the resources held here, otherwise they
+ * must be held until the mount table update is complete
+ */
+ mnt_file = mfp;
+#else /* not MOUNT_TABLE_ON_FILE */
+ endmntent(mfp);
+#endif /* not MOUNT_TABLE_ON_FILE */
+
+ return mhp;
+}