Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e6b8bc09 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: Add sanity check to make_indexed_dir 

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.

Thanks to Sami Liedes for reporting this bug.

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



Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
parent 06a279d6

fs/ext4/namei.c

+15 −6
Original line number Diff line number Diff line
@@ -1368,7 +1368,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry, 
	struct fake_dirent *fde;



	blocksize =  dir->i_sb->s_blocksize;

	dxtrace(printk(KERN_DEBUG "Creating index\n"));

	dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));

	retval = ext4_journal_get_write_access(handle, bh);

	if (retval) {

		ext4_std_error(dir->i_sb, retval);
@@ -1377,6 +1377,20 @@ 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 ext4_dir_entry_2 *)((char *)fde +

		ext4_rec_len_from_disk(fde->rec_len));

	if ((char *) de >= (((char *) root) + blocksize)) {

		ext4_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;



	/* Allocate new block for the 0th block's dirents */

	bh2 = ext4_append(handle, dir, &block, &retval);

	if (!(bh2)) {

		brelse(bh);
@@ -1385,11 +1399,6 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry, 
	EXT4_I(dir)->i_flags |= EXT4_INDEX_FL;

	data1 = bh2->b_data;



	/* The 0th block becomes the root, move the dirents out */

	fde = &root->dotdot;

	de = (struct ext4_dir_entry_2 *)((char *)fde +

		ext4_rec_len_from_disk(fde->rec_len));

	len = ((char *) root) + blocksize - (char *) de;

	memcpy (data1, de, len);

	de = (struct ext4_dir_entry_2 *) data1;

	top = data1 + len;