Ard Biesheuvel 3e03dca500 efi: Mark all EFI runtime services as unsupported on non-EFI boot
Recent changes to the way we deal with EFI runtime services that
are marked as unsupported by the firmware resulted in a regression
for non-EFI boot. The problem is that all EFI runtime services are
marked as available by default, and any non-NULL checks on the EFI
service function pointers (which will be non-NULL even for runtime
services that are unsupported on an EFI boot) were replaced with
checks against the mask stored in efi.runtime_supported_mask.

When doing a non-EFI boot, this check against the mask will return
a false positive, given the fact that all runtime services are
marked as enabled by default. Since we dropped the non-NULL check
of the runtime service function pointer in favor of the mask check,
we will now unconditionally dereference the function pointer, even
if it is NULL, and go boom.

So let's ensure that the mask reflects reality on a non-EFI boot,
which is that all EFI runtime services are unsupported.

Reported-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20200228121408.9075-7-ardb@kernel.org
2020-02-29 10:16:57 +01:00
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2020-02-09 16:05:50 -08:00
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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