[PATCH v1] efi/runtime-wrappers: Avoid crashing on early PRM code invocations

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

There is a dependency between EFI and ACPI PRM that the latter cannot
run until the former is ready and PRM can be invoked from AML early
through acpi_platformrt_space_handler().  If that happens before
initializing efi_rts_wq, it leads to a NULL pointer dereference.

Avoid that by adding an efi_rts_wq check against NULL to
efi_call_acpi_prm_handler().

Fixes: 5894cf571e14 ("acpi/prmt: Use EFI runtime sandbox to invoke PRM handlers")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: 6.6+ <stable@vger.kernel.org> # 6.6+
---

An alternative would be to somehow ensure that efisubsys_init() will always
run before acpi_init(), but moving any of them to another initcall level is
not an option AFAICS.

---
 drivers/firmware/efi/runtime-wrappers.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -590,6 +590,8 @@ efi_call_acpi_prm_handler(efi_status_t (
 
 	if (down_interruptible(&efi_runtime_lock))
 		return EFI_ABORTED;
+	if (!efi_rts_wq)
+		return EFI_NOT_READY;
 	status = efi_queue_work(ACPI_PRM_HANDLER, handler_addr,
 				param_buffer_addr, context);
 	up(&efi_runtime_lock);