From: Amir Goldstein amir73il@gmail.com
commit 9c6d8f13e9da10a26ad7f0a020ef86e8ef142835 upstream.
On non-samefs overlay without xino, non pure upper inodes should use a pseudo_dev assigned to each unique lower fs and pure upper inodes use the real upper st_dev.
It is fine for an overlay pure upper inode to use the same st_dev;st_ino values as the real upper inode, because the content of those two different filesystem objects is always the same.
In this case, however: - two filesystems, A and B - upper layer is on A - lower layer 1 is also on A - lower layer 2 is on B
Non pure upper overlay inode, whose origin is in layer 1 will have the same st_dev;st_ino values as the real lower inode. This may result with a false positive results of 'diff' between the real lower and copied up overlay inode.
Fix this by using the upper st_dev;st_ino values in this case. This breaks the property of constant st_dev;st_ino across copy up of this case. This breakage will be fixed by a later patch.
Fixes: 5148626b806a ("ovl: allocate anon bdev per unique lower fs") Cc: stable@vger.kernel.org # v4.17+ Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/overlayfs/inode.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -203,8 +203,14 @@ int ovl_getattr(const struct path *path, if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) || (!ovl_verify_lower(dentry->d_sb) && (is_dir || lowerstat.nlink == 1))) { - stat->ino = lowerstat.ino; lower_layer = ovl_layer_lower(dentry); + /* + * Cannot use origin st_dev;st_ino because + * origin inode content may differ from overlay + * inode content. + */ + if (samefs || lower_layer->fsid) + stat->ino = lowerstat.ino; }
/*