Unionfs: ensure consistent lower inodes types

When looking up a lower object in multiple branches, especially for
directories, ignore any existing entries whose type is different than the
type of the first found object (otherwise we'll be trying to, say, call
readdir on a non-dir inode).

Signed-off-by: Himanshu Kanda <hkanda@fsl.cs.sunysb.edu>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>

diff --git a/fs/unionfs/lookup.c b/fs/unionfs/lookup.c
index b9ee072c52d9cdebc7f05079c6323389463d8352..755158e9ce28717cd0b37da5a457cd1e807d7660 100644 (file)
--- a/fs/unionfs/lookup.c
+++ b/fs/unionfs/lookup.c
@@ -256,6 +256,19 @@ struct dentry *unionfs_lookup_backend(struct dentry *dentry,
                        continue;
                }
 
+               /*
+                * If we already found at least one positive dentry
+                * (dentry_count is non-zero), then we skip all remaining
+                * positive dentries if their type is a non-dir.  This is
+                * because only directories are allowed to stack on multiple
+                * branches, but we have to skip non-dirs (to avoid, say,
+                * calling readdir on a regular file).
+                */
+               if (!S_ISDIR(lower_dentry->d_inode->i_mode) && dentry_count) {
+                       dput(lower_dentry);
+                       continue;
+               }
+
                /* number of positive dentries */
                dentry_count++;