bug#21372: [PATCH] df: fix prioritize real mounts over bind mounts

[Dave Chiluk]

Fixes an issue where bind mounts with shorter mount directories than the
original mount are prioritized when running df.  The root cause of this
is that /proc/self/mountinfo now lists the filesystem device with bind
mounts rather than the source directory. With /etc/mtab the source
device was listed as the originating directory so this was not an issue.

More information is available here.
https://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/1432871
---
 src/df.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/df.c b/src/df.c
index 2e541b9..00c77c1 100644
--- a/src/df.c
+++ b/src/df.c
@@ -652,9 +652,14 @@ filter_mount_list (bool devices_only)
               else if ((strchr (me->me_devname, '/')
                        /* let "real" devices with '/' in the name win.  */
                         && ! strchr (devlist->me->me_devname, '/'))
-                       /* let a shorter mountdir win.  */
-                       || (strlen (devlist->me->me_mountdir)
+                       /* let a shorter mountdir win. */
+                       /* Only if it's not a bind mount. */
+                       || ((strlen (devlist->me->me_mountdir)
                            > strlen (me->me_mountdir))
+                          && (devlist->me->me_mntroot != NULL
+                             && me->me_mntroot != NULL
+                             && (strlen (devlist->me->me_mntroot)
+                                 > strlen(me->me_mntroot))))
                        /* let an entry overmounted on a new device win...  */
                        || (! STREQ (devlist->me->me_devname, me->me_devname)
                            /* ... but only when matching an existing mnt point,
-- 
1.9.1