ovl: Fix opaque regression in ovl_lookup

Current multi-layer support overlayfs has a regression in
.lookup(). If there is a directory in upperdir and a regular
file has same name in lowerdir in a merged directory, lower
file is hidden and upper directory is set to opaque in former
case. But it is changed in present code.

In lowerdir lookup path, if a found inode is not directory,
the type checking of previous inode is missing. This inode
will be copied to the lowerstack of ovl_entry directly.

That will lead to several wrong conditions, for example,
the reading of the directory in upperdir may return an error
like:

   ls: reading directory .: Not a directory

This patch makes the lowerdir lookup path check the opaque
for non-directory file too.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6ca8ea8..9e94f4a 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -372,7 +372,6 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                bool opaque = false;
                struct path lowerpath = poe->lowerstack[i];
 
-               opaque = false;
                this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
                err = PTR_ERR(this);
                if (IS_ERR(this)) {
@@ -395,20 +394,24 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 */
                if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
                        opaque = true;
-               /*
-                * If this is a non-directory then stop here.
-                *
-                * FIXME: check for opaqueness maybe better done in remove code.
-                */
-               if (!S_ISDIR(this->d_inode->i_mode)) {
-                       opaque = true;
-               } else if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
-                                   !S_ISDIR(this->d_inode->i_mode))) {
+
+               if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
+                            !S_ISDIR(this->d_inode->i_mode))) {
+                       /*
+                        * FIXME: check for upper-opaqueness maybe better done
+                        * in remove code.
+                        */
                        if (prev == upperdentry)
                                upperopaque = true;
                        dput(this);
                        break;
                }
+               /*
+                * If this is a non-directory then stop here.
+                */
+               if (!S_ISDIR(this->d_inode->i_mode))
+                       opaque = true;
+
                stack[ctr].dentry = this;
                stack[ctr].mnt = lowerpath.mnt;
                ctr++;