Code:  static int ext4_convert_unwritten_extents_endio(handle_t *handle,
					      struct inode *inode,
					      struct ext4_ext_path *path)
 {
 	struct ext4_extent *ex;
 	int depth;
 	int err = 0;
 
 	depth = ext_depth(inode);
 	ex = path[depth].p_ext;
 
 	ext_debug("ext4_convert_unwritten_extents_endio: inode %lu, logical"
 		"block %llu, max_blocks %u\n", inode->i_ino,
		(unsigned long long)le32_to_cpu(ex->ee_block),
		ext4_ext_get_actual_len(ex));
 
 	err = ext4_ext_get_access(handle, inode, path + depth);
 	if (err)
		goto out;
	/* first mark the extent as initialized */
	ext4_ext_mark_initialized(ex);

	/* note: ext4_ext_correct_indexes() isn't needed here because
	 * borders are not changed
	 */
	ext4_ext_try_to_merge(handle, inode, path, ex);

	/* Mark modified extent as dirty */
	err = ext4_ext_dirty(handle, inode, path + path->p_depth);
out:
	ext4_ext_show_leaf(inode, path);
	return err;
}

Vulnerability Type: +Info 
CWE ID: CWE-362
Summary: Race condition in fs/ext4/extents.c in the Linux kernel before 3.4.16 allows local users to obtain sensitive information from a deleted file by reading an extent that was not properly marked as uninitialized.
Commit Message: ext4: race-condition protection for ext4_convert_unwritten_extents_endio

We assumed that at the time we call ext4_convert_unwritten_extents_endio()
extent in question is fully inside [map.m_lblk, map->m_len] because
it was already split during submission.  But this may not be true due to
a race between writeback vs fallocate.

If extent in question is larger than requested we will split it again.
Special precautions should being done if zeroout required because
[map.m_lblk, map->m_len] already contains valid data.

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