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Subject[patch 25/32] ext3: Add sanity check to make_indexed_dir
2.6.27-stable review patch.  If anyone has any objections, please let us know.

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

commit a21102b55c4f8dfd3adb4a15a34cd62237b46039 upstream.

Make sure the rec_len field in the '..' entry is sane, lest we overrun
the directory block and cause a kernel oops on a purposefully
corrupted filesystem.

This fixes a bug related to a bug originally reported by Sami Liedes
for ext4 at:

http://bugzilla.kernel.org/show_bug.cgi?id=12430

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ext3/namei.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
--- a/fs/ext3/namei.c
+++ b/fs/ext3/namei.c
@@ -1374,7 +1374,7 @@ static int make_indexed_dir(handle_t *ha
struct fake_dirent *fde;

blocksize = dir->i_sb->s_blocksize;
- dxtrace(printk("Creating index\n"));
+ dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));
retval = ext3_journal_get_write_access(handle, bh);
if (retval) {
ext3_std_error(dir->i_sb, retval);
@@ -1383,6 +1383,19 @@ static int make_indexed_dir(handle_t *ha
}
root = (struct dx_root *) bh->b_data;

+ /* The 0th block becomes the root, move the dirents out */
+ fde = &root->dotdot;
+ de = (struct ext3_dir_entry_2 *)((char *)fde +
+ ext3_rec_len_from_disk(fde->rec_len));
+ if ((char *) de >= (((char *) root) + blocksize)) {
+ ext3_error(dir->i_sb, __func__,
+ "invalid rec_len for '..' in inode %lu",
+ dir->i_ino);
+ brelse(bh);
+ return -EIO;
+ }
+ len = ((char *) root) + blocksize - (char *) de;
+
bh2 = ext3_append (handle, dir, &block, &retval);
if (!(bh2)) {
brelse(bh);
@@ -1391,11 +1404,6 @@ static int make_indexed_dir(handle_t *ha
EXT3_I(dir)->i_flags |= EXT3_INDEX_FL;
data1 = bh2->b_data;

- /* The 0th block becomes the root, move the dirents out */
- fde = &root->dotdot;
- de = (struct ext3_dir_entry_2 *)((char *)fde +
- ext3_rec_len_from_disk(fde->rec_len));
- len = ((char *) root) + blocksize - (char *) de;
memcpy (data1, de, len);
de = (struct ext3_dir_entry_2 *) data1;
top = data1 + len;


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