[PATCH v2] mount: mount--move with mtab support fix

[Roman Borisov]

added new update_mtab_entry() function to update /etc/mtab when new mounted
entry is created by mount--move. In such case update_mtab_entry() is used in
mount.c/mount_it_now() function instead of addmntent().

fixes: http://lists.busybox.net/pipermail/busybox/2011-January/074510.html

v2: added #if ENABLE_FEATURE_MTAB_SUPPORT in functions declarations;
added ENABLE_FEATURE_CLEAN_UP condition check for cleaning

Signed-off-by: Roman Borisov <ext-roman.borisov at nokia.com>
---
 include/libbb.h    |    3 ++
 libbb/mtab.c       |   54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 util-linux/mount.c |    6 +++-
 3 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/include/libbb.h b/include/libbb.h
index 587a5f9..7cbe0a1 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1099,7 +1099,10 @@ extern void run_applet_no_and_exit(int a, char **argv) NORETURN FAST_FUNC;
 extern int match_fstype(const struct mntent *mt, const char *fstypes) FAST_FUNC;
 extern struct mntent *find_mount_point(const char *name, int subdir_too) FAST_FUNC;
 #endif
+#if ENABLE_FEATURE_MTAB_SUPPORT
 extern void erase_mtab(const char * name) FAST_FUNC;
+extern void update_mtab_entry(const struct mntent *mp) FAST_FUNC;
+#endif
 extern unsigned int tty_baud_to_value(speed_t speed) FAST_FUNC;
 extern speed_t tty_value_to_baud(unsigned int value) FAST_FUNC;
 #if ENABLE_DESKTOP
diff --git a/libbb/mtab.c b/libbb/mtab.c
index 22bff64..3af9379 100644
--- a/libbb/mtab.c
+++ b/libbb/mtab.c
@@ -52,4 +52,58 @@ void FAST_FUNC erase_mtab(const char *name)
 	} else if (errno != EROFS)
 		bb_perror_msg(bb_path_mtab_file);
 }
+
+/*
+update_mtab_entry() is used to update entry in case of mount--move.
+we are looking for existing entries mnt_dir which is equal to mnt_fsname of
+input mntent and replace it by new one.
+*/
+void FAST_FUNC update_mtab_entry(const struct mntent *mp)
+{
+        struct mntent *entries, *m;
+        int i, count;
+        FILE *mountTable;
+
+        mountTable = setmntent(bb_path_mtab_file, "r");
+        if (!mountTable) {
+                bb_perror_msg(bb_path_mtab_file);
+                return;
+        }
+
+        entries = NULL;
+        count = 0;
+        while ((m = getmntent(mountTable)) != 0) {
+                entries = xrealloc_vector(entries, 3, count);
+                entries[count].mnt_fsname = xstrdup(m->mnt_fsname);
+                entries[count].mnt_dir = xstrdup(m->mnt_dir);
+                entries[count].mnt_type = xstrdup(m->mnt_type);
+                entries[count].mnt_opts = xstrdup(m->mnt_opts);
+                entries[count].mnt_freq = m->mnt_freq;
+                entries[count].mnt_passno = m->mnt_passno;
+                count++;
+        }
+        endmntent(mountTable);
+
+        mountTable = setmntent(bb_path_mtab_file, "w");
+        if (mountTable) {
+                for (i = 0; i < count; i++) {
+                        if (strcmp(entries[i].mnt_dir, mp->mnt_fsname) != 0)
+                                addmntent(mountTable, &entries[i]);
+                        else
+                                addmntent(mountTable, mp);
+                }
+                endmntent(mountTable);
+        } else if (errno != EROFS)
+                bb_perror_msg(bb_path_mtab_file);
+
+       if (ENABLE_FEATURE_CLEAN_UP) {
+               for (i = 0; i < count; i++) {
+                       free(entries[i].mnt_fsname);
+                       free(entries[i].mnt_dir);
+                       free(entries[i].mnt_type);
+                       free(entries[i].mnt_opts);
+               }
+       }
+}
 #endif
+
diff --git a/util-linux/mount.c b/util-linux/mount.c
index 0f213bb..c0c828b 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -524,8 +524,10 @@ static int mount_it_now(struct mntent *mp, long vfsflags, char *filteropts)
 		mp->mnt_freq = mp->mnt_passno = 0;
 
 		// Write and close.
-
-		addmntent(mountTable, mp);
+                if (vfsflags & MS_MOVE)
+                        update_mtab_entry(mp);
+                else
+                        addmntent(mountTable, mp);
 		endmntent(mountTable);
 		if (ENABLE_FEATURE_CLEAN_UP) {
 			free(mp->mnt_dir);
-- 
1.7.0.4