CIFS: Fix symbolic links usage

Now we treat any reparse point as a symbolic link and map it to a Unix
one that is not true in a common case due to many reparse point types
supported by SMB servers.

Distinguish reparse point types into two groups:
1) that can be accessed directly through a reparse point
(junctions, deduplicated files, NFS symlinks);
2) that need to be processed manually (Windows symbolic links, DFS);

and map only Windows symbolic links to Unix ones.

Cc: <stable@vger.kernel.org>
Acked-by: Jeff Layton <jlayton@redhat.com>
Reported-and-tested-by: Joao Correia <joaomiguelcorreia@gmail.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 8 insertions, 32 deletions

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 53a75f3d0179..5940ecabbe6a 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -134,22 +134,6 @@ 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)
 {
@@ -159,27 +143,19 @@ 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 if (fattr->cf_cifsattrs & ATTR_REPARSE) {
-                fattr->cf_mode = S_IFLNK;
-                fattr->cf_dtype = DT_LNK;
         } else {
                 fattr->cf_mode = S_IFREG | cifs_sb->mnt_file_mode;
                 fattr->cf_dtype = DT_REG;
         }
 
+        /*
+         * We need to revalidate it further to make a decision about whether it
+         * is a symbolic link, DFS referral or a reparse point with a direct
+         * access like junctions, deduplicated files, NFS symlinks.
+         */
+        if (fattr->cf_cifsattrs & ATTR_REPARSE)
+                fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
+
         /* non-unix readdir doesn't provide nlink */
         fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;