Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759339AbZGAAbt (ORCPT ); Tue, 30 Jun 2009 20:31:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759650AbZGAAaD (ORCPT ); Tue, 30 Jun 2009 20:30:03 -0400 Received: from kroah.org ([198.145.64.141]:34316 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759341AbZGAAaA (ORCPT ); Tue, 30 Jun 2009 20:30:00 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Tue Jun 30 17:03:57 2009 Message-Id: <20090701000357.276381426@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Tue, 30 Jun 2009 16:59:51 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jan Kara , Subject: [patch 07/30] jbd: fix race in buffer processing in commit code References: <20090630235944.868879272@mini.kroah.org> Content-Disposition: inline; filename=jbd-fix-race-in-buffer-processing-in-commit-code.patch In-Reply-To: <20090701002817.GA6156@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2099 Lines: 48 2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Jan Kara commit a61d90d75d0f9e86432c45b496b4b0fbf0fd03dc upstream. In commit code, we scan buffers attached to a transaction. During this scan, we sometimes have to drop j_list_lock and then we recheck whether the journal buffer head didn't get freed by journal_try_to_free_buffers(). But checking for buffer_jbd(bh) isn't enough because a new journal head could get attached to our buffer head. So add a check whether the journal head remained the same and whether it's still at the same transaction and list. This is a nasty bug and can cause problems like memory corruption (use after free) or trigger various assertions in JBD code (observed). Signed-off-by: Jan Kara Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/jbd/commit.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/jbd/commit.c +++ b/fs/jbd/commit.c @@ -238,7 +238,7 @@ write_out_data: spin_lock(&journal->j_list_lock); } /* Someone already cleaned up the buffer? */ - if (!buffer_jbd(bh) + if (!buffer_jbd(bh) || bh2jh(bh) != jh || jh->b_transaction != commit_transaction || jh->b_jlist != BJ_SyncData) { jbd_unlock_bh_state(bh); @@ -463,7 +463,9 @@ void journal_commit_transaction(journal_ spin_lock(&journal->j_list_lock); continue; } - if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) { + if (buffer_jbd(bh) && bh2jh(bh) == jh && + jh->b_transaction == commit_transaction && + jh->b_jlist == BJ_Locked) { __journal_unfile_buffer(jh); jbd_unlock_bh_state(bh); journal_remove_journal_head(bh); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/