ACPICA: Disassembler: Enhance resource descriptor detection

ACPICA commit ba5020b2dbe1538e4ccd7ac2dfd8843a690c007f

This change enhances the detection of resource descriptors
within a buffer object. For the end_tag opcode, the second byte
is defined to be either a checksum or zero. All known ASL compilers
insert a zero for this byte. The disassembler now ensures this
byte is zero before deciding that a buffer should be disassembled
to a resource descriptor. This helps eliminate incorrect decisions
when attempting to disassemble a buffer to a resource descriptor.

Link: https://github.com/acpica/acpica/commit/ba5020b2
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/utresrc.c b/drivers/acpi/acpica/utresrc.c
index ff096d9755b9..e0587c85bafd 100644
--- a/drivers/acpi/acpica/utresrc.c
+++ b/drivers/acpi/acpica/utresrc.c
@@ -474,6 +474,15 @@ acpi_ut_walk_aml_resources(struct acpi_walk_state *walk_state,
                                 return_ACPI_STATUS(AE_AML_NO_RESOURCE_END_TAG);
                         }
 
+                        /*
+                         * The end_tag opcode must be followed by a zero byte.
+                         * Although this byte is technically defined to be a checksum,
+                         * in practice, all ASL compilers set this byte to zero.
+                         */
+                        if (*(aml + 1) != 0) {
+                                return_ACPI_STATUS(AE_AML_NO_RESOURCE_END_TAG);
+                        }
+
                         /* Return the pointer to the end_tag if requested */
 
                         if (!user_function) {