ovl: check for bad and whiteout index on lookup

[sfrench/cifs-2.6.git] / fs / overlayfs / namei.c

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 9bc0e580a5b3fa44dbacd26ec0196e1ec4bd282b..8aef2b304b2d2bd2ad0c26942765e4bca0362835 100644 (file)
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -397,8 +397,19 @@ int ovl_verify_index(struct dentry *index, struct path *lowerstack,
        if (!d_inode(index))
                return 0;
 
-       err = -EISDIR;
-       if (d_is_dir(index))
+       /*
+        * Directory index entries are going to be used for looking up
+        * redirected upper dirs by lower dir fh when decoding an overlay
+        * file handle of a merge dir. Whiteout index entries are going to be
+        * used as an indication that an exported overlay file handle should
+        * be treated as stale (i.e. after unlink of the overlay inode).
+        * We don't know the verification rules for directory and whiteout
+        * index entries, because they have not been implemented yet, so return
+        * EROFS if those entries are found to avoid corrupting an index that
+        * was created by a newer kernel.
+        */
+       err = -EROFS;
+       if (d_is_dir(index) || ovl_is_whiteout(index))
                goto fail;
 
        err = -EINVAL;
@@ -436,8 +447,8 @@ out:
        return err;
 
 fail:
-       pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, err=%i)\n",
-                           index, err);
+       pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, ftype=%x, err=%i)\n",
+                           index, d_inode(index)->i_mode & S_IFMT, err);
        goto out;
 }
 
@@ -502,6 +513,7 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
                goto out;
        }
 
+       inode = d_inode(index);
        if (d_is_negative(index)) {
                if (upper && d_inode(origin)->i_nlink > 1) {
                        pr_warn_ratelimited("overlayfs: hard link with origin but no index (ino=%lu).\n",
@@ -511,11 +523,22 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
 
                dput(index);
                index = NULL;
-       } else if (upper && d_inode(index) != d_inode(upper)) {
-               inode = d_inode(index);
-               pr_warn_ratelimited("overlayfs: wrong index found (index ino: %lu, upper ino: %lu).\n",
-                                   d_inode(index)->i_ino,
-                                   d_inode(upper)->i_ino);
+       } else if (upper && d_inode(upper) != inode) {
+               pr_warn_ratelimited("overlayfs: wrong index found (index=%pd2, ino=%lu, upper ino=%lu).\n",
+                                   index, inode->i_ino, d_inode(upper)->i_ino);
+               goto fail;
+       } else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
+                  ((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
+               /*
+                * Index should always be of the same file type as origin
+                * except for the case of a whiteout index. A whiteout
+                * index should only exist if all lower aliases have been
+                * unlinked, which means that finding a lower origin on lookup
+                * whose index is a whiteout should be treated as an error.
+                */
+               pr_warn_ratelimited("overlayfs: bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n",
+                                   index, d_inode(index)->i_mode & S_IFMT,
+                                   d_inode(origin)->i_mode & S_IFMT);
                goto fail;
        }