From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla-daemon@bugzilla.kernel.org Subject: [Bug 45631] Caught 32-bit read from uninitialized memory in ext4_da_get_block_prep Date: Sun, 5 Aug 2012 22:21:05 +0000 (UTC) Message-ID: <20120805222105.05B4011FC6A@bugzilla.kernel.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" To: linux-ext4@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.19.201]:35325 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754972Ab2HEWVI (ORCPT ); Sun, 5 Aug 2012 18:21:08 -0400 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0B740201CD for ; Sun, 5 Aug 2012 22:21:07 +0000 (UTC) Received: from bugzilla.kernel.org (unknown [198.145.19.217]) by mail.kernel.org (Postfix) with ESMTP id 422B5201AC for ; Sun, 5 Aug 2012 22:21:06 +0000 (UTC) In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: https://bugzilla.kernel.org/show_bug.cgi?id=45631 Theodore Tso changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |tytso@mit.edu --- Comment #1 from Theodore Tso 2012-08-05 22:21:04 --- It's a false positive in that this isn't going to actually cause an actual bug; we're just saving and restoring an uninitialized value if we have a error. The fact that we do this is no big deal, since if i_da_metadata_calc_len is zero, the value of i_data_metadata_calc_last_lblock is never consulted. So if we save an uninitialized value, and then later restore it, it really doesn't matter from a correctness point of view. That being said, triggering a kmemcheck failure is sad, even if it's not a real bug, so I agree we should fix it. The most expedient and most efficient fix is to simply initialize i_data_metadata_calc_last_lblock to zero in ext4_alloc_inode(); this is where we initialize i_data_metadata_calc_len to zero, and if we initialize the last_lblock to zero, it won't matter, and it saves us from having to adding an extra conditional in ext4_da_get_block_prep(). - Ted -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug.