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Date: Thu, 25 Oct 2012 08:41:41 +0200
From: Petr Matousek <>
Subject: CVE-2012-4508 -- kernel: ext4: AIO vs fallocate stale data exposure

A race condition flaw has been found in the way asynchronous I/O and
fallocate interacted which can lead to exposure of stale data -- that
is, an extent which should have had the "uninitialized" bit set
indicating that its blocks have not yet been written and thus contain
data from a deleted file. An unprivileged local user could use this flaw
to cause an information leak.


Red Hat would like to thank Theodore Tso for reporting this issue.
Upstream acknowledges Dmitry Monakhov as the original reporter.

Upstream fix:;a=commitdiff;h=dee1f973ca341c266229faa5a1a5bb268bed3531

Please see for
further information regarding the patch.


Petr Matousek / Red Hat Security Response Team

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