linux-kernel - IMA + O_DIRECT (Re: [PATCH 0/1] fix IMA + Apparmor kernel panic)

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Date:	Fri, 09 May 2014 12:10:03 +0900
From:	"J. R. Okajima" <hooanon05g@...il.com>
To:	Dmitry Kasatkin <d.kasatkin@...sung.com>
Cc:	viro@...iv.linux.org.uk, ebiederm@...ssion.com,
	linux-security-module@...r.kernel.org, eparis@...hat.com,
	zohar@...ux.vnet.ibm.com, dmitry.kasatkin@...il.com,
	linux-kernel@...r.kernel.org
Subject: IMA + O_DIRECT (Re: [PATCH 0/1] fix IMA + Apparmor kernel panic)

Dmitry Kasatkin:
> Following patch replaces IMA usage of kernel_read() with special
> version which skips security check that triggers kernel panic
> when Apparmor and IMA appraisal are enabled together.

I know this is related to exit(2), but this behaviour of IMA is related
to open(2) too.
When O_DIRECT is specified, some filesystems (for example, ext2) call
do_blockdev_direct_IO() which acquires i_mutex. But
IMA:process_measurement() already acquires i_mutex before kernel_read().
It causes a deadlock even if you replace kernel_read() by a simpler one.
How can we stop reading the file from IMA?

J. R. Okajima
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