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>

1 files changed, 13 insertions, 10 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6ca8ea8cb9b2..9e94f4acef1a 100644
--- 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++;