update umount procedure

If umount(8) supports --fake and --no-canonicalize (util-linux-ng
version 2.18 or later), and umount(2) supports the UMOUNT_NOFOLLOW
flag (linux kernel version 2.6.35 or later) then, "fusermount -u" will
call the umount(2) system call and use "umount --fake ..." to update
/etc/mtab

Added --disable-legacy-umount option to configure.  This disables the
runtime checking of umount(8) version.  When built with this option
then "fusermount -u" will fail if umount(8) doesn't support the --fake
and --no-canonicalize options.

diff --git a/ChangeLog b/ChangeLog
index b6bcda36280f8e0ceb93d3114dd99d22edb8ada7..5ce455c278267ba51dcf847cab9860a1cc159217 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,17 @@
        * Open /dev/null for write instead of read for redirecting stdout
        and stderr
 
+       * If umount(8) supports --fake and --no-canonicalize (util-linux-ng
+       version 2.18 or later), and umount(2) supports the
+       UMOUNT_NOFOLLOW flag (linux kernel version 2.6.35 or later)  then,
+       "fusermount -u" will call the umount(2) system call and use
+       "umount --fake ..." to update /etc/mtab
+
+       * Added --disable-legacy-umount option to configure.  This
+       disables the runtime checking of umount(8) version.  When built
+       with this option then "fusermount -u" will fail if umount(8)
+       doesn't support the --fake and --no-canonicalize options.
+
 2010-10-14  Miklos Szeredi <miklos@szeredi.hu>
 
        * Use LTLIBICONV when linking libfuse.  This fixes building against

diff --git a/configure.in b/configure.in
index 3b6451103e9137e5fc8064cc28ebfd0228f850a6..846868ae191181df45776f9feb31d45c715150ea 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -33,6 +33,8 @@ AC_ARG_ENABLE(example,
        [  --enable-example        Compile with examples ])
 AC_ARG_ENABLE(mtab,
        [  --disable-mtab          Disable and ignore usage of /etc/mtab ])
+AC_ARG_ENABLE(legacy-umount,
+       [  --disable-legacy-umount If umount(8) is util-linux-ng >= 2.18 ])
 
 AC_ARG_WITH(pkgconfigdir,
             [  --with-pkgconfigdir=DIR      pkgconfig file in DIR @<:@LIBDIR/pkgconfig@:>@],
@@ -54,6 +56,11 @@ fi
 if test "$enable_mtab" = "no"; then
        AC_DEFINE(IGNORE_MTAB, 1, [Don't update /etc/mtab])
 fi
+
+if test "$enable_legacy_umount" != "no"; then
+       AC_DEFINE(LEGACY_UMOUNT, 1, [Enable legacy umount support])
+fi
+
 AC_CHECK_FUNCS([fork setxattr fdatasync])
 AC_CHECK_MEMBERS([struct stat.st_atim])
 AC_CHECK_MEMBERS([struct stat.st_atimespec])

diff --git a/lib/mount_util.c b/lib/mount_util.c
index 25b7e436906252b307fe34186e999b6e56f85622..edbba1215af58ce9185dde90239b75b99ebf02ae 100644 (file)
--- a/lib/mount_util.c
+++ b/lib/mount_util.c
@@ -262,6 +262,55 @@ int fuse_mnt_umount(const char *progname, const char *abs_mnt,
        return exec_umount(progname, rel_mnt, lazy);
 }
 
+static int remove_mount(const char *progname, const char *mnt)
+{
+       int res;
+       int status;
+       sigset_t blockmask;
+       sigset_t oldmask;
+
+       sigemptyset(&blockmask);
+       sigaddset(&blockmask, SIGCHLD);
+       res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
+       if (res == -1) {
+               fprintf(stderr, "%s: sigprocmask: %s\n", progname, strerror(errno));
+               return -1;
+       }
+
+       res = fork();
+       if (res == -1) {
+               fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
+               goto out_restore;
+       }
+       if (res == 0) {
+               sigprocmask(SIG_SETMASK, &oldmask, NULL);
+               setuid(geteuid());
+               execl("/bin/umount", "/bin/umount", "--no-canonicalize", "-i",
+                     "--fake", mnt, NULL);
+               fprintf(stderr, "%s: failed to execute /bin/umount: %s\n",
+                       progname, strerror(errno));
+               exit(1);
+       }
+       res = waitpid(res, &status, 0);
+       if (res == -1)
+               fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
+
+       if (status != 0)
+               res = -1;
+
+ out_restore:
+       sigprocmask(SIG_SETMASK, &oldmask, NULL);
+       return res;
+}
+
+int fuse_mnt_remove_mount(const char *progname, const char *mnt)
+{
+       if (!mtab_needs_update(mnt))
+               return 0;
+
+       return remove_mount(progname, mnt);
+}
+
 char *fuse_mnt_resolve_path(const char *progname, const char *orig)
 {
        char buf[PATH_MAX];

diff --git a/lib/mount_util.h b/lib/mount_util.h
index f392f99f17a7129cc78233073aef0a9c656f533c..dc5c916f128a2789ddbc175b3b0716e12715b00c 100644 (file)
--- a/lib/mount_util.h
+++ b/lib/mount_util.h
@@ -10,6 +10,7 @@
 
 int fuse_mnt_add_mount(const char *progname, const char *fsname,
                       const char *mnt, const char *type, const char *opts);
+int fuse_mnt_remove_mount(const char *progname, const char *mnt);
 int fuse_mnt_umount(const char *progname, const char *abs_mnt,
                    const char *rel_mnt, int lazy);
 char *fuse_mnt_resolve_path(const char *progname, const char *orig);

diff --git a/util/fusermount.c b/util/fusermount.c
index 39da9b6a0b6fa1f36d6e1a1a5d28c0fbbe64570f..3b4125ead1f7d4a31c8c3525d369426c143e3144 100644 (file)
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -45,6 +45,16 @@
 #define MS_PRIVATE (1<<18)
 #endif
 
+#ifndef UMOUNT_DETACH
+#define UMOUNT_DETACH  0x00000002      /* Just detach from the tree */
+#endif
+#ifndef UMOUNT_NOFOLLOW
+#define UMOUNT_NOFOLLOW        0x00000008      /* Don't follow symlink on umount */
+#endif
+#ifndef UMOUNT_UNUSED
+#define UMOUNT_UNUSED  0x80000000      /* Flag guaranteed to be unused */
+#endif
+
 static const char *progname;
 
 static int user_allow_other = 0;
@@ -380,19 +390,13 @@ static int chdir_to_parent(char *copy, const char **lastp, int *currdir_fd)
        return 0;
 }
 
-static int unmount_fuse_locked(const char *mnt, int quiet, int lazy)
+static int unmount_fuse_legacy(const char *mnt, int lazy)
 {
        int currdir_fd = -1;
        char *copy;
        const char *last;
        int res;
 
-       if (getuid() != 0) {
-               res = may_unmount(mnt, quiet);
-               if (res == -1)
-                       return -1;
-       }
-
        copy = strdup(mnt);
        if (copy == NULL) {
                fprintf(stderr, "%s: failed to allocate memory\n", progname);
@@ -419,6 +423,140 @@ out:
        return res;
 }
 
+static int unmount_fuse_nofollow(const char *mnt, int quiet, int lazy)
+{
+       int res;
+       int umount_flags = UMOUNT_NOFOLLOW;
+
+       if (lazy)
+               umount_flags |= UMOUNT_DETACH;
+
+       res = umount2(mnt, umount_flags);
+       if (res == -1) {
+               if (!quiet) {
+                       fprintf(stderr, "%s: failed to unmount %s: %s\n",
+                               progname, mnt, strerror(errno));
+               }
+               return -1;
+       }
+
+       return fuse_mnt_remove_mount(progname, mnt);
+}
+
+/* Check whether the kernel supports UMOUNT_NOFOLLOW flag */
+static int umount_nofollow_support(void)
+{
+       int res = umount2("", UMOUNT_UNUSED);
+       if (res != -1 || errno != EINVAL)
+               return 0;
+
+       res = umount2("", UMOUNT_NOFOLLOW);
+       if (res != -1 || errno != ENOENT)
+               return 0;
+
+       return 1;
+}
+
+#ifdef LEGACY_UMOUNT
+/* Check if umount(8) supports "--fake" and "--no-canonicalize" options */
+static int umount_fake_support(void)
+{
+       int res;
+       int status;
+       sigset_t blockmask;
+       sigset_t oldmask;
+       int pip[2];
+       char buf[1024];
+       char *s;
+       unsigned majver;
+       unsigned minver;
+       int supported = 0;
+       int pid;
+
+       res = pipe(pip);
+       if (res == -1)
+               return 0;
+
+       sigemptyset(&blockmask);
+       sigaddset(&blockmask, SIGCHLD);
+       res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
+       if (res == -1)
+               goto out_close;
+
+       pid = fork();
+       if (pid == -1)
+               goto out_restore;
+
+       if (pid == 0) {
+               int nullfd;
+
+               close(pip[0]);
+               dup2(pip[1], 1);
+               if (pip[1] != 1)
+                       close(pip[1]);
+               nullfd = open("/dev/null", O_WRONLY);
+               dup2(nullfd, 2);
+               sigprocmask(SIG_SETMASK, &oldmask, NULL);
+               setuid(getuid());
+               execl("/bin/umount", "/bin/umount", "--version", NULL);
+               exit(1);
+       }
+       res = read(pip[0], buf, sizeof(buf));
+       if (res == -1 || res == sizeof(buf))
+               buf[0] = '\0';
+       else
+               buf[res] = '\0';
+
+       res = waitpid(pid, &status, 0);
+       if (res == -1 || status != 0)
+               goto out_restore;
+
+       s = strstr(buf, "util-linux-ng ");
+       if (s == NULL)
+               goto out_restore;
+
+       s += 14;
+       if (sscanf(s, "%u.%u", &majver, &minver) < 2)
+               goto out_restore;
+
+       if (majver < 2 || (majver == 2 && minver < 18))
+               goto out_restore;
+
+       supported = 1;
+
+out_restore:
+       sigprocmask(SIG_SETMASK, &oldmask, NULL);
+out_close:
+       close(pip[0]);
+       close(pip[1]);
+
+       return supported;
+}
+#else
+static int umount_fake_support(void)
+{
+       return 1;
+}
+#endif
+
+static int unmount_fuse_locked(const char *mnt, int quiet, int lazy)
+{
+       int res;
+
+       if (getuid() != 0) {
+               res = may_unmount(mnt, quiet);
+               if (res == -1)
+                       return -1;
+       }
+
+       if (umount_nofollow_support() && umount_fake_support())
+               res = unmount_fuse_nofollow(mnt, quiet, lazy);
+       else
+               res = unmount_fuse_legacy(mnt, lazy);
+
+       return res;
+}
+
 static int unmount_fuse(const char *mnt, int quiet, int lazy)
 {
        int res;
@@ -1073,7 +1211,7 @@ static int mount_fuse(const char *mnt, const char *opts)
        if (geteuid() == 0) {
                res = add_mount(source, mnt, type, mnt_opts);
                if (res == -1) {
-                       umount2(mnt, 2); /* lazy umount */
+                       umount2(mnt, UMOUNT_DETACH); /* lazy umount */
                        close(fd);
                        return -1;
                }
@@ -1231,7 +1369,7 @@ int main(int argc, char *argv[])
                if (geteuid() == 0)
                        res = unmount_fuse(mnt, quiet, lazy);
                else {
-                       res = umount2(mnt, lazy ? 2 : 0);
+                       res = umount2(mnt, lazy ? UMOUNT_DETACH : 0);
                        if (res == -1 && !quiet)
                                fprintf(stderr,
                                        "%s: failed to unmount %s: %s\n",