ext4: only use i_size_high for regular files

Directories are not allowed to be bigger than 2GB, so don't use
i_size_high for anything other than regular files.  E2fsck should
complain about these inodes, but the simplest thing to do for the
kernel is to only use i_size_high for regular files.

This prevents an intentially corrupted filesystem from causing the
kernel to burn a huge amount of CPU and issuing error messages such
as:

EXT4-fs warning (device loop0): ext4_block_to_path: block 135090028 > max

Thanks to David Maciejak from Fortinet's FortiGuard Global Security
Research Team for reporting this issue.

http://bugzilla.kernel.org/show_bug.cgi?id=12375

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a6444cee0c7e..49484ba801c9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -360,9 +360,9 @@ static int ext4_block_to_path(struct inode *inode,
 		final = ptrs;
 	} else {
 		ext4_warning(inode->i_sb, "ext4_block_to_path",
-				"block %lu > max",
+				"block %lu > max in inode %lu",
 				i_block + direct_blocks +
-				indirect_blocks + double_blocks);
+				indirect_blocks + double_blocks, inode->i_ino);
 	}
 	if (boundary)
 		*boundary = final - 1 - (i_block & (ptrs - 1));