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: 28321582334c261c ("arm64: initialize ptrauth keys for kernel booting task")
Signed-off-by: Mark Rutland <[email protected]>
Reported-by: Will Deacon <[email protected]>
Cc: Amit Daniel Kachhap <[email protected]>
Cc: Marc Zyngier <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>
Tested-by: Will Deacon <[email protected]>

0 files changed, 0 insertions, 0 deletions