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Mark Rutland 3fabb43818 arm64: sync kernel APIAKey when installing
A direct write to a APxxKey_EL1 register requires a context
synchronization event to ensure that indirect reads made by subsequent
instructions (e.g. AUTIASP, PACIASP) observe the new value.

When we initialize the boot task's APIAKey in boot_init_stack_canary()
via ptrauth_keys_switch_kernel() we miss the necessary ISB, and so there
is a window where instructions are not guaranteed to use the new APIAKey
value. This has been observed to result in boot-time crashes where
PACIASP and AUTIASP within a function used a mixture of the old and new
key values.

Fix this by having ptrauth_keys_switch_kernel() synchronize the new key
value with an ISB. At the same time, __ptrauth_key_install() is renamed
to __ptrauth_key_install_nosync() so that it is obvious that this
performs no synchronization itself.

Fixes: 2832158233 ("arm64: initialize ptrauth keys for kernel booting task")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Will Deacon <will@kernel.org>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Will Deacon <will@kernel.org>
History 2020-04-21 15:52:56 +01:00
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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.