udf: Check length of extended attributes and allocation descriptors

commit 23b133bd upstream.

Check length of extended attributes and allocation descriptors when
loading inodes from disk. Otherwise corrupted filesystems could confuse
the code and make the kernel oops.

This fixes CVE-2015-4167.
Reported-by: Carl Henrik Lunde <chlunde@ping.uio.no>
Signed-off-by: Jan Kara <jack@suse.cz>
[Use make_bad_inode() instead of branching due to older implementation.]
Signed-off-by: Chas Williams <3chas3@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/udf/inode.c

@@ -1496,6 +1496,22 @@ static void udf_fill_inode(struct inode *inode, struct buffer_head *bh)
 		iinfo->i_checkpoint = le32_to_cpu(efe->checkpoint);
 	}
 
+	/*
+	 * Sanity check length of allocation descriptors and extended attrs to
+	 * avoid integer overflows
+	 */
+	if (iinfo->i_lenEAttr > inode->i_sb->s_blocksize
+			|| iinfo->i_lenAlloc > inode->i_sb->s_blocksize) {
+		make_bad_inode(inode);
+		return;
+	}
+	/* Now do exact checks */
+	if (udf_file_entry_alloc_offset(inode)
+			+ iinfo->i_lenAlloc > inode->i_sb->s_blocksize) {
+		make_bad_inode(inode);
+		return;
+	}
+
 	switch (fe->icbTag.fileType) {
 	case ICBTAG_FILE_TYPE_DIRECTORY:
 		inode->i_op = &udf_dir_inode_operations;