[patch 35/39] ext4: only use i_size_high for regular files

[Greg KH <gregkh@suse.de>]

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2.6.28-stable review patch.  If anyone has any objections, please let us know.

------------------

From: "Theodore Ts'o" <tytso@mit.edu>

(cherry picked from commit 06a279d636734da32bb62dd2f7b0ade666f65d7c)

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/ext4/ext4.h  |    7 +++++--
 fs/ext4/inode.c |    4 ++--
 2 files changed, 7 insertions(+), 4 deletions(-)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1188,8 +1188,11 @@ static inline void ext4_r_blocks_count_s
 
 static inline loff_t ext4_isize(struct ext4_inode *raw_inode)
 {
-	return ((loff_t)le32_to_cpu(raw_inode->i_size_high) << 32) |
-		le32_to_cpu(raw_inode->i_size_lo);
+	if (S_ISREG(le16_to_cpu(raw_inode->i_mode)))
+		return ((loff_t)le32_to_cpu(raw_inode->i_size_high) << 32) |
+			le32_to_cpu(raw_inode->i_size_lo);
+	else
+		return (loff_t) le32_to_cpu(raw_inode->i_size_lo);
 }
 
 static inline void ext4_isize_set(struct ext4_inode *raw_inode, loff_t i_size)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -351,9 +351,9 @@ static int ext4_block_to_path(struct ino
 		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));