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Date: Thu, 23 Feb 2012 19:11:01 +0100
From: Petr Matousek <>
Subject: CVE request -- kernel: block: CLONE_IO io_context refcounting issues

With CLONE_IO, copy_io() increments both ioc->refcount and
ioc->nr_tasks. However exit_io_context() only decrements
ioc->refcount if ioc->nr_tasks reaches 0.

With CLONE_IO, parent's io_context->nr_tasks is incremented, but never
decremented whenever copy_process() fails afterwards, which prevents
exit_io_context() from calling IO schedulers exit functions.

An unprivileged local user could use these flaws cause denial of

Upstream fixes:


Looks like it got fixed in Linux kernel 2.6.33(-rc1).

Petr Matousek / Red Hat Security Response Team

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