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ext3: Add sanity check to make_indexed_dir

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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>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2009-01-16 11:13:47 -05:00
parent e6b8bc09ba
commit a21102b55c
1 changed files with 14 additions and 6 deletions
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20
fs/ext3/namei.c
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@ -1358,7 +1358,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
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);
@ -1367,6 +1367,19 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
}
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);
@ -1375,11 +1388,6 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
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;