ext4: don't verify checksums of dx non-leaf nodes during fallback scan

During a directory entry lookup of a hashed directory, if the
hash-based lookup functions fail and we fall back to a linear scan,
don't try to verify the dirent checksum on the internal nodes of the
hash tree because they don't store a checksum in a hidden dirent like
the leaf nodes do.

Reported-by: George Spelvin <linux@horizon.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 580af3dfc0eb..88e9a2c7e328 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1146,6 +1146,21 @@ static inline int search_dirblock(struct buffer_head *bh,
         return 0;
 }
 
+static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
+                               struct ext4_dir_entry *de)
+{
+        struct super_block *sb = dir->i_sb;
+
+        if (!is_dx(dir))
+                return 0;
+        if (block == 0)
+                return 1;
+        if (de->inode == 0 &&
+            ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize) ==
+                        sb->s_blocksize)
+                return 1;
+        return 0;
+}
 
 /*
  *      ext4_find_entry()
@@ -1246,6 +1261,8 @@ restart:
                         goto next;
                 }
                 if (!buffer_verified(bh) &&
+                    !is_dx_internal_node(dir, block,
+                                         (struct ext4_dir_entry *)bh->b_data) &&
                     !ext4_dirent_csum_verify(dir,
                                 (struct ext4_dir_entry *)bh->b_data)) {
                         EXT4_ERROR_INODE(dir, "checksumming directory "