linux-kernel - [ 005/180] jbd2: clear BH_Delay & BH_Unwritten in journal_unmap

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Date:	Tue, 02 Oct 2012 00:52:02 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Eric Sandeen <sandeen@...hat.com>, "Theodore Tso" <tytso@....edu>,
	Stefan Bader <stefan.bader@...onical.com>,
	Willy Tarreau <w@....eu>
Subject: [ 005/180] jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@...hat.com>

commit 15291164b22a357cb211b618adfef4fa82fc0de3 upstream.

journal_unmap_buffer()'s zap_buffer: code clears a lot of buffer head
state ala discard_buffer(), but does not touch _Delay or _Unwritten as
discard_buffer() does.

This can be problematic in some areas of the ext4 code which assume
that if they have found a buffer marked unwritten or delay, then it's
a live one.  Perhaps those spots should check whether it is mapped
as well, but if jbd2 is going to tear down a buffer, let's really
tear it down completely.

Without this I get some fsx failures on sub-page-block filesystems
up until v3.2, at which point 4e96b2dbbf1d7e81f22047a50f862555a6cb87cb
and 189e868fa8fdca702eb9db9d8afc46b5cb9144c9 make the failures go
away, because buried within that large change is some more flag
clearing.  I still think it's worth doing in jbd2, since
->invalidatepage leads here directly, and it's the right place
to clear away these flags.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Cc: stable@...r.kernel.org

BugLink: http://bugs.launchpad.net/bugs/929781
CVE-2011-4086

Signed-off-by: Stefan Bader <stefan.bader@...onical.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/jbd2/transaction.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a051270..5c156ad 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1822,6 +1822,8 @@ zap_buffer_unlocked:
 	clear_buffer_mapped(bh);
 	clear_buffer_req(bh);
 	clear_buffer_new(bh);
+	clear_buffer_delay(bh);
+	clear_buffer_unwritten(bh);
 	bh->b_bdev = NULL;
 	return may_free;
 }
-- 
1.7.2.1.45.g54fbc



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