Merge tag 'acpi-4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull ACPI fixes from Rafael Wysocki:
"These revert an ACPICA commit from the 4.11 cycle that causes problems
to happen on some systems and add a protection against possible kernel
crashes due to table reference counter imbalance.
Specifics:
- Revert a 4.11 ACPICA change that made assumptions which are not
satisfied on some systems and caused the enumeration of resources
to fail on them (Rafael Wysocki).
- Add a mechanism to prevent tables from being unmapped prematurely
due to reference counter overflows (Lv Zheng)"
* tag 'acpi-4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPICA: Tables: Mechanism to handle late stage acpi_get_table() imbalance
Revert "ACPICA: Disassembler: Enhance resource descriptor detection"
diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c
index 7abe665..0d2e989 100644
--- a/drivers/acpi/acpica/tbutils.c
+++ b/drivers/acpi/acpica/tbutils.c
@@ -416,9 +416,18 @@ acpi_tb_get_table(struct acpi_table_desc *table_desc,
}
}
- table_desc->validation_count++;
- if (table_desc->validation_count == 0) {
- table_desc->validation_count--;
+ if (table_desc->validation_count < ACPI_MAX_TABLE_VALIDATIONS) {
+ table_desc->validation_count++;
+
+ /*
+ * Detect validation_count overflows to ensure that the warning
+ * message will only be printed once.
+ */
+ if (table_desc->validation_count >= ACPI_MAX_TABLE_VALIDATIONS) {
+ ACPI_WARNING((AE_INFO,
+ "Table %p, Validation count overflows\n",
+ table_desc));
+ }
}
*out_table = table_desc->pointer;
@@ -445,13 +454,20 @@ void acpi_tb_put_table(struct acpi_table_desc *table_desc)
ACPI_FUNCTION_TRACE(acpi_tb_put_table);
- if (table_desc->validation_count == 0) {
- ACPI_WARNING((AE_INFO,
- "Table %p, Validation count is zero before decrement\n",
- table_desc));
- return_VOID;
+ if (table_desc->validation_count < ACPI_MAX_TABLE_VALIDATIONS) {
+ table_desc->validation_count--;
+
+ /*
+ * Detect validation_count underflows to ensure that the warning
+ * message will only be printed once.
+ */
+ if (table_desc->validation_count >= ACPI_MAX_TABLE_VALIDATIONS) {
+ ACPI_WARNING((AE_INFO,
+ "Table %p, Validation count underflows\n",
+ table_desc));
+ return_VOID;
+ }
}
- table_desc->validation_count--;
if (table_desc->validation_count == 0) {
diff --git a/drivers/acpi/acpica/utresrc.c b/drivers/acpi/acpica/utresrc.c
index e0587c8..ff096d9 100644
--- a/drivers/acpi/acpica/utresrc.c
+++ b/drivers/acpi/acpica/utresrc.c
@@ -474,15 +474,6 @@ 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) {
diff --git a/include/acpi/actbl.h b/include/acpi/actbl.h
index d92543f..bdc55c0 100644
--- a/include/acpi/actbl.h
+++ b/include/acpi/actbl.h
@@ -374,6 +374,20 @@ struct acpi_table_desc {
u16 validation_count;
};
+/*
+ * Maximum value of the validation_count field in struct acpi_table_desc.
+ * When reached, validation_count cannot be changed any more and the table will
+ * be permanently regarded as validated.
+ *
+ * This is to prevent situations in which unbalanced table get/put operations
+ * may cause premature table unmapping in the OS to happen.
+ *
+ * The maximum validation count can be defined to any value, but should be
+ * greater than the maximum number of OS early stage mapping slots to avoid
+ * leaking early stage table mappings to the late stage.
+ */
+#define ACPI_MAX_TABLE_VALIDATIONS ACPI_UINT16_MAX
+
/* Masks for Flags field above */
#define ACPI_TABLE_ORIGIN_EXTERNAL_VIRTUAL (0) /* Virtual address, external maintained */
