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vfs: rename: check backing inode being equal

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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+
This commit is contained in:
Miklos Szeredi 2016-05-11 01:16:37 +02:00 committed by Al Viro
parent 54d5ca871e
commit 9409e22acd
1 changed files with 5 additions and 1 deletions
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6
fs/namei.c
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@ -4213,7 +4213,11 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
if (source == target)
/*
* Check source == target.
* On overlayfs need to look at underlying inodes.
*/
if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0))
return 0;
error = may_delete(old_dir, old_dentry, is_dir);