CVE-2011-4086 jbd2: unmapped buffer with _Unwritten or _Delay flags set can lead to DoS (rhbz 788260)

1 files changed, 91 insertions, 0 deletions

diff --git a/jbd2-clear-BH_Delay-and-BH_Unwritten-in-journal_unmap_buf.patch b/jbd2-clear-BH_Delay-and-BH_Unwritten-in-journal_unmap_buf.patch
new file mode 100644
index 000000000..5ea8ccc10
--- /dev/null
+++ b/jbd2-clear-BH_Delay-and-BH_Unwritten-in-journal_unmap_buf.patch
@@ -0,0 +1,91 @@
+Path: news.gmane.org!not-for-mail
+From: Eric Sandeen <sandeen@redhat.com>
+Newsgroups: gmane.comp.file-systems.ext4
+Subject: [PATCH] jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer
+Date: Tue, 07 Feb 2012 16:07:20 -0600
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+
+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>
+Cc: stable@vger.kernel.org
+---
+
+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;
+ }
+
+
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