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-   -   jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer (http://www.linux-archive.org/ubuntu-kernel-team/657959-jbd2-clear-bh_delay-bh_unwritten-journal_unmap_buffer.html)

Eric Sandeen 02-20-2012 09:53 PM

jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer
 
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@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

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

(cherry-picked from 15291164b22a357cb211b618adfef4fa82fc0de3 upstream)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
---
fs/jbd2/transaction.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 35ae096..52653306 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1949,6 +1949,8 @@ 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;
}
--
1.7.9.5


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