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Mimi Zohar 4f0496d8ff ima: based on policy warn about loading firmware (pre-allocated buffer) 
Some systems are memory constrained but they need to load very large
firmwares.  The firmware subsystem allows drivers to request this
firmware be loaded from the filesystem, but this requires that the
entire firmware be loaded into kernel memory first before it's provided
to the driver.  This can lead to a situation where we map the firmware
twice, once to load the firmware into kernel memory and once to copy the
firmware into the final resting place.

To resolve this problem, commit a098ecd2fa ("firmware: support loading
into a pre-allocated buffer") introduced request_firmware_into_buf() API
that allows drivers to request firmware be loaded directly into a
pre-allocated buffer.

Do devices using pre-allocated memory run the risk of the firmware being
accessible to the device prior to the completion of IMA's signature
verification any more than when using two buffers? (Refer to mailing list
discussion[1]).

Only on systems with an IOMMU can the access be prevented.  As long as
the signature verification completes prior to the DMA map is performed,
the device can not access the buffer.  This implies that the same buffer
can not be re-used.  Can we ensure the buffer has not been DMA mapped
before using the pre-allocated buffer?

[1] https://lkml.org/lkml/2018/7/10/56

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>
 		2018-07-16 12:31:57 -07:00
..
evm Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-06-07 15:40:37 -07:00
ima ima: based on policy warn about loading firmware (pre-allocated buffer) 2018-07-16 12:31:57 -07:00
Kconfig security: integrity: Remove select to deleted option PUBLIC_KEY_ALGO_RSA 2016-04-12 19:54:58 +01:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
digsig.c integrity/security: fix digsig.c build error with header file 2018-02-22 20:09:08 -08:00
digsig_asymmetric.c integrity: Small code improvements 2017-06-21 14:37:12 -04:00
iint.c integrity: Add an integrity directory in securityfs 2018-05-17 08:03:07 -04:00
integrity.h integrity: Add an integrity directory in securityfs 2018-05-17 08:03:07 -04:00
integrity_audit.c audit: use inline function to get audit context 2018-05-14 17:24:18 -04:00