oss-security - CVE request -- kernel: cifs: dentry refcount leak when opening a FIFO on lookup leads to panic on unmount

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Message-ID: <20120228151501.GH4015@dhcp-25-225.brq.redhat.com>
Date: Tue, 28 Feb 2012 16:15:02 +0100
From: Petr Matousek <pmatouse@...hat.com>
To: oss-security@...ts.openwall.com
Subject: CVE request -- kernel: cifs: dentry refcount leak when opening a
 FIFO on lookup leads to panic on unmount

The cifs code will attempt to open files on lookup under certain
circumstances. What happens though if we find that the file we opened
was actually a FIFO or other special file? Currently, the open
filehandle just ends up being leaked leading to a dentry refcount
mismatch and oops on umount.

An unprivileged local user could use this flaw to crash the system.

Introduced by:
a6ce4932fbdbcd8f8e8c6df76812014351c32892 (Linux kernel 2.6.31)

Proposed upstream patch:
http://thread.gmane.org/gmane.linux.kernel.cifs/5526

References:
https://bugzilla.redhat.com/show_bug.cgi?id=798293
http://thread.gmane.org/gmane.linux.kernel.cifs/5526

Thanks,
-- 
Petr Matousek / Red Hat Security Response Team

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