tree 94f5f543f75ed4080b99483242ef7622c97d6f54
parent 54d5ca871e72f2bb172ec9323497f01cd5091ec7
author Miklos Szeredi <mszeredi@redhat.com> 1462922197 +0200
committer Al Viro <viro@zeniv.linux.org.uk> 1462938943 -0400

vfs: rename: check backing inode being equal

If a file is renamed to a hardlink of itself POSIX specifies that rename(2)
should do nothing and return success.

This condition is checked in vfs_rename().  However it won't detect hard
links on overlayfs where these are given separate inodes on the overlayfs
layer.

Overlayfs itself detects this condition and returns success without doing
anything, but then vfs_rename() will proceed as if this was a successful
rename (detach_mounts(), d_move()).

The correct thing to do is to detect this condition before even calling
into overlayfs.  This patch does this by calling vfs_select_inode() to get
the underlying inodes.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v4.2+