mount: support -i; pass through -f and -n to helpers as necessary

function                                             old     new   delta
mount_it_now                                         298     345     +47
singlemount                                          776     772      -4

Signed-off-by: Colin Watson <cjwatson@ubuntu.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 49 insertions, 27 deletions

diff --git a/include/usage.h b/include/usage.h
index 0f6378e06..c6006aa65 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -2901,6 +2901,9 @@
      "\n        -f              Dry run" \
         ) \
         ) \
+        IF_FEATURE_MOUNT_HELPERS( \
+     "\n        -i              Don't run mount helper" \
+        ) \
         IF_FEATURE_MTAB_SUPPORT( \
      "\n        -n              Don't update /etc/mtab" \
         ) \
diff --git a/util-linux/mount.c b/util-linux/mount.c
index ab249642b..72dabd840 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -79,15 +79,21 @@ enum {
 };
 
 #if ENABLE_FEATURE_MTAB_SUPPORT
-#define useMtab (!(option_mask32 & OPT_n))
+#define USE_MTAB (!(option_mask32 & OPT_n))
 #else
-#define useMtab 0
+#define USE_MTAB 0
 #endif
 
 #if ENABLE_FEATURE_MOUNT_FAKE
-#define fakeIt (option_mask32 & OPT_f)
+#define FAKE_IT (option_mask32 & OPT_f)
 #else
-#define fakeIt 0
+#define FAKE_IT 0
+#endif
+
+#if ENABLE_FEATURE_MOUNT_HELPERS
+#define HELPERS_ALLOWED (!(option_mask32 & OPT_i))
+#else
+#define HELPERS_ALLOWED 0
 #endif
 
 
@@ -360,7 +366,7 @@ static llist_t *get_block_backed_filesystems(void)
                 "/proc/filesystems",
         };
         char *fs, *buf;
-        llist_t *list = 0;
+        llist_t *list = NULL;
         int i;
         FILE *f;
 
@@ -369,10 +375,11 @@ static llist_t *get_block_backed_filesystems(void)
                 if (!f) continue;
 
                 while ((buf = xmalloc_fgetline(f)) != NULL) {
-                        if (!strncmp(buf, "nodev", 5) && isspace(buf[5]))
+                        if (strncmp(buf, "nodev", 5) == 0 && isspace(buf[5]))
                                 continue;
                         fs = skip_whitespace(buf);
-                        if (*fs=='#' || *fs=='*' || !*fs) continue;
+                        if (*fs == '#' || *fs == '*' || !*fs)
+                                continue;
 
                         llist_add_to_end(&list, xstrdup(fs));
                         free(buf);
@@ -398,7 +405,7 @@ static int mount_it_now(struct mntent *mp, long vfsflags, char *filteropts)
 {
         int rc = 0;
 
-        if (fakeIt) {
+        if (FAKE_IT) {
                 if (verbose >= 2)
                         bb_error_msg("would do mount('%s','%s','%s',0x%08lx,'%s')",
                                 mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
@@ -414,11 +421,15 @@ static int mount_it_now(struct mntent *mp, long vfsflags, char *filteropts)
 
                 // If mount failed, try
                 // helper program mount.<mnt_type>
-                if (ENABLE_FEATURE_MOUNT_HELPERS && rc) {
-                        char *args[6];
+                if (HELPERS_ALLOWED && rc) {
+                        char *args[8];
                         int errno_save = errno;
                         args[0] = xasprintf("mount.%s", mp->mnt_type);
                         rc = 1;
+                        if (FAKE_IT)
+                                args[rc++] = (char *)"-f";
+                        if (ENABLE_FEATURE_MTAB_SUPPORT && !USE_MTAB)
+                                args[rc++] = (char *)"-n";
                         args[rc++] = mp->mnt_fsname;
                         args[rc++] = mp->mnt_dir;
                         if (filteropts) {
@@ -449,7 +460,7 @@ static int mount_it_now(struct mntent *mp, long vfsflags, char *filteropts)
         // If the mount was successful, and we're maintaining an old-style
         // mtab file by hand, add the new entry to it now.
  mtab:
-        if (useMtab && !rc && !(vfsflags & MS_REMOUNT)) {
+        if (USE_MTAB && !rc && !(vfsflags & MS_REMOUNT)) {
                 char *fsname;
                 FILE *mountTable = setmntent(bb_path_mtab_file, "a+");
                 const char *option_str = mount_option_str;
@@ -1570,8 +1581,8 @@ static int singlemount(struct mntent *mp, int ignore_busy)
 {
         int rc = -1;
         long vfsflags;
-        char *loopFile = 0, *filteropts = 0;
-        llist_t *fl = 0;
+        char *loopFile = NULL, *filteropts = NULL;
+        llist_t *fl = NULL;
         struct stat st;
 
         vfsflags = parse_mount_options(mp->mnt_opts, &filteropts);
@@ -1581,21 +1592,28 @@ static int singlemount(struct mntent *mp, int ignore_busy)
                 mp->mnt_type = NULL;
 
         // Might this be a virtual filesystem?
-        if (ENABLE_FEATURE_MOUNT_HELPERS
-         && (strchr(mp->mnt_fsname, '#'))
-        ) {
-                char *s, *p, *args[35];
-                int n = 0;
-// FIXME: does it allow execution of arbitrary commands?!
-// What args[0] can end up with?
-                for (s = p = mp->mnt_fsname; *s && n < 35-3; ++s) {
-                        if (s[0] == '#' && s[1] != '#') {
-                                *s = '\0';
-                                args[n++] = p;
-                                p = s + 1;
+        if (ENABLE_FEATURE_MOUNT_HELPERS && strchr(mp->mnt_fsname, '#')) {
+                char *args[35];
+                char *s;
+                int n;
+                // fsname: "cmd#arg1#arg2..."
+                // WARNING: allows execution of arbitrary commands!
+                // Try "mount 'sh#-c#sh' bogus_dir".
+                // It is safe ONLY because non-root
+                // cannot use two-argument mount command
+                // and using one-argument "mount 'sh#-c#sh'" doesn't work:
+                // "mount: can't find sh#-c#sh in /etc/fstab"
+                // (if /etc/fstab has it, it's ok: root sets up /etc/fstab).
+
+                s = mp->mnt_fsname;
+                n = 0;
+                args[n++] = s;
+                while (*s && n < 35 - 2) {
+                        if (*s++ == '#' && *s != '#') {
+                                s[-1] = '\0';
+                                args[n++] = s;
                         }
                 }
-                args[n++] = p;
                 args[n++] = mp->mnt_dir;
                 args[n] = NULL;
                 rc = wait4pid(xspawn(args));
@@ -1704,7 +1722,8 @@ static int singlemount(struct mntent *mp, int ignore_busy)
                 for (fl = fslist; fl; fl = fl->link) {
                         mp->mnt_type = fl->data;
                         rc = mount_it_now(mp, vfsflags, filteropts);
-                        if (!rc) break;
+                        if (!rc)
+                                break;
                 }
         }