fix mountpoint test to not prevemt mkfs_xxx from making image in any file

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 23 insertions, 16 deletions

diff --git a/libbb/find_mount_point.c b/libbb/find_mount_point.c
index 12b2cfce4..bcb18effe 100644
--- a/libbb/find_mount_point.c
+++ b/libbb/find_mount_point.c
@@ -17,27 +17,29 @@
  * Given any other file (or directory), find the mount table entry for its
  * filesystem.
  */
-struct mntent* FAST_FUNC find_mount_point(const char *name)
+struct mntent* FAST_FUNC find_mount_point(const char *name, int subdir_too)
 {
         struct stat s;
-        dev_t mountDevice;
-        FILE *mountTable;
+        FILE *mtab_fp;
         struct mntent *mountEntry;
+        dev_t devno_of_name;
+        bool block_dev;
 
         if (stat(name, &s) != 0)
                 return NULL;
 
-        if (S_ISBLK(s.st_mode))
-                mountDevice = s.st_rdev;
-        else
-                mountDevice = s.st_dev;
-
+        devno_of_name = s.st_dev;
+        block_dev = 0;
+        if (S_ISBLK(s.st_mode)) {
+                devno_of_name = s.st_rdev;
+                block_dev = 1;
+        }
 
-        mountTable = setmntent(bb_path_mtab_file, "r");
-        if (!mountTable)
-                return 0;
+        mtab_fp = setmntent(bb_path_mtab_file, "r");
+        if (!mtab_fp)
+                return NULL;
 
-        while ((mountEntry = getmntent(mountTable)) != NULL) {
+        while ((mountEntry = getmntent(mtab_fp)) != NULL) {
                 /* rootfs mount in Linux 2.6 exists always,
                  * and it makes sense to always ignore it.
                  * Otherwise people can't reference their "real" root! */
@@ -49,13 +51,18 @@ struct mntent* FAST_FUNC find_mount_point(const char *name)
                 ) { /* String match. */
                         break;
                 }
-                /* Match the device. */
-                if (stat(mountEntry->mnt_fsname, &s) == 0 && s.st_rdev == mountDevice)
+
+                if (!(subdir_too || block_dev))
+                        continue;
+
+                /* Is device's dev_t == name's dev_t? */
+                if (stat(mountEntry->mnt_fsname, &s) == 0 && s.st_rdev == devno_of_name)
                         break;
                 /* Match the directory's mount point. */
-                if (stat(mountEntry->mnt_dir, &s) == 0 && s.st_dev == mountDevice)
+                if (stat(mountEntry->mnt_dir, &s) == 0 && s.st_dev == devno_of_name)
                         break;
         }
-        endmntent(mountTable);
+        endmntent(mtab_fp);
+
         return mountEntry;
 }