1 files changed, 29 insertions, 0 deletions

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 770d5a9781c1..94d620198209 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -126,6 +126,22 @@ out:
         dput(dentry);
 }
 
+/*
+ * Is it possible that this directory might turn out to be a DFS referral
+ * once we go to try and use it?
+ */
+static bool
+cifs_dfs_is_possible(struct cifs_sb_info *cifs_sb)
+{
+#ifdef CONFIG_CIFS_DFS_UPCALL
+        struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+
+        if (tcon->Flags & SMB_SHARE_IS_IN_DFS)
+                return true;
+#endif
+        return false;
+}
+
 static void
 cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
 {
@@ -135,6 +151,19 @@ cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
         if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
                 fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
                 fattr->cf_dtype = DT_DIR;
+                /*
+                 * Windows CIFS servers generally make DFS referrals look
+                 * like directories in FIND_* responses with the reparse
+                 * attribute flag also set (since DFS junctions are
+                 * reparse points). We must revalidate at least these
+                 * directory inodes before trying to use them (if
+                 * they are DFS we will get PATH_NOT_COVERED back
+                 * when queried directly and can then try to connect
+                 * to the DFS target)
+                 */
+                if (cifs_dfs_is_possible(cifs_sb) &&
+                    (fattr->cf_cifsattrs & ATTR_REPARSE))
+                        fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
         } else {
                 fattr->cf_mode = S_IFREG | cifs_sb->mnt_file_mode;
                 fattr->cf_dtype = DT_REG;