[PATCH] ACPI: Add absent field_obj null check

[Alexey Simakov <bigalex934@gmail.com>]

The acpi_ev_address_space_dispatch function is designed
in such way that assignning field_obj to NULL is valid case.

Cover the missed execution path with this check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 0acf24ad7e10 ("ACPICA: Add support for PCC Opregion special context data")
Signed-off-by: Alexey Simakov <bigalex934@gmail.com>
---
 drivers/acpi/acpica/evregion.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/acpica/evregion.c b/drivers/acpi/acpica/evregion.c
index fa3475da7ea9..fa01bcd3840d 100644
--- a/drivers/acpi/acpica/evregion.c
+++ b/drivers/acpi/acpica/evregion.c
@@ -163,7 +163,7 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
 			return_ACPI_STATUS(AE_NOT_EXIST);
 		}
 
-		if (region_obj->region.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
+		if (field_obj && region_obj->region.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
 			struct acpi_pcc_info *ctx =
 			    handler_desc->address_space.context;
 
-- 
2.34.1

Just FYI, this patch was already merged to github ACPICA repository.
Commit hash with correspond changes at ACPICA repository: f421dd9dd897dfd1e0c015afa90cd0de2464e23c