diff options
| -rw-r--r-- | drivers/acpi/acpica/tbutils.c | 34 | ||||
| -rw-r--r-- | include/acpi/actbl.h | 14 |
2 files changed, 39 insertions, 9 deletions
diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c index 7abe66505739..0d2e98920069 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/include/acpi/actbl.h b/include/acpi/actbl.h index d92543f3bbfd..bdc55c0da19c 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 */ |