From: Miklos Szeredi Date: Mon, 8 Nov 2010 15:00:16 +0000 (+0100) Subject: update umount procedure X-Git-Tag: fuse_2_9_0~99 X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=eba226948b44d5a303a10908d440e808eaf0bae6;p=qemu-gpiodev%2Flibfuse.git 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 b6bcda3..5ce455c 100644 --- 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 * Use LTLIBICONV when linking libfuse. This fixes building against diff --git a/configure.in b/configure.in index 3b64511..846868a 100644 --- 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 25b7e43..edbba12 100644 --- 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 f392f99..dc5c916 100644 --- 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 39da9b6..3b4125e 100644 --- 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",