From ae6b3e54aa52cd29965b8e4e47000ed2c5d78eb8 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Sun, 18 Nov 2018 20:25:35 +0100 Subject: [PATCH] ACPICA: Fix handling of buffer-size in acpi_ex_write_data_to_field() Generic Serial Bus transfers use a data struct like this: struct gsb_buffer { u8 status; u8 len; u8 data[0]; }; acpi_ex_write_data_to_field() copies the data which is to be written from the source-buffer to a temp-buffer. This is done because the OpReg-handler overwrites the status field and some transfers do a write + read-back. Commit f99b89eefeb6 ("ACPICA: Update for generic_serial_bus and attrib_raw_process_bytes protocol") acpi_ex_write_data_to_field() introduces a number of problems with this: 1) It drops a "length += 2" statement used to calculate the temp-buffer size causing the temp-buffer to only be 1/2 bytes large for byte/word transfers while it should be 3/4 bytes (taking the status and len field into account). This is already fixed in commit e324e10109fc ("ACPICA: Update for field unit access") which refactors the code. The ACPI 6.0 spec (ACPI_6.0.pdf) "5.5.2.4.5.2 Declaring and Using a GenericSerialBusData Buffer" (page 232) states that the GenericSerialBus Data Buffer Length field is only valid when doing a Read/Write Block (AttribBlock) transfer, but since the troublesome commit we unconditionally use the len field to determine how much data to copy from the source-buffer into the temp-buffer passed to the OpRegion. This causes 3 further issues: 2) This may lead to not copying enough data to the temp-buffer causing the OpRegion handler for the serial-bus to write garbage to the hardware. 3) The temp-buffer passed to the OpRegion is allocated to the size returned by acpi_ex_get_serial_access_length(), which may be as little as 1, so potentially this may lead to a write overflow of the temp-buffer. 4) Commit e324e10109fc ("ACPICA: Update for field unit access") drops a length check on the source-buffer, leading to a potential read overflow of the source-buffer. This commit fixes all 3 remaining issues by not looking at the len field at all (the interpretation of this field is left up to the OpRegion handler), and copying the minimum of the source- and temp-buffer sizes from the source-buffer to the temp-buffer. This fixes e.g. an Acer S1003 no longer booting since the troublesome commit. Fixes: f99b89eefeb6 (ACPICA: Update for generic_serial_bus and ...) Fixes: e324e10109fc (ACPICA: Update for field unit access) Signed-off-by: Hans de Goede Signed-off-by: Rafael J. Wysocki --- drivers/acpi/acpica/exserial.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-) diff --git a/drivers/acpi/acpica/exserial.c b/drivers/acpi/acpica/exserial.c index 0d42f30e5b25..9920fac6413f 100644 --- a/drivers/acpi/acpica/exserial.c +++ b/drivers/acpi/acpica/exserial.c @@ -244,7 +244,6 @@ acpi_ex_write_serial_bus(union acpi_operand_object *source_desc, { acpi_status status; u32 buffer_length; - u32 data_length; void *buffer; union acpi_operand_object *buffer_desc; u32 function; @@ -282,14 +281,12 @@ acpi_ex_write_serial_bus(union acpi_operand_object *source_desc, case ACPI_ADR_SPACE_SMBUS: buffer_length = ACPI_SMBUS_BUFFER_SIZE; - data_length = ACPI_SMBUS_DATA_SIZE; function = ACPI_WRITE | (obj_desc->field.attribute << 16); break; case ACPI_ADR_SPACE_IPMI: buffer_length = ACPI_IPMI_BUFFER_SIZE; - data_length = ACPI_IPMI_DATA_SIZE; function = ACPI_WRITE; break; @@ -310,7 +307,6 @@ acpi_ex_write_serial_bus(union acpi_operand_object *source_desc, /* Add header length to get the full size of the buffer */ buffer_length += ACPI_SERIAL_HEADER_SIZE; - data_length = source_desc->buffer.pointer[1]; function = ACPI_WRITE | (accessor_type << 16); break; @@ -318,20 +314,6 @@ acpi_ex_write_serial_bus(union acpi_operand_object *source_desc, return_ACPI_STATUS(AE_AML_INVALID_SPACE_ID); } -#if 0 - OBSOLETE ? - /* Check for possible buffer overflow */ - if (data_length > source_desc->buffer.length) { - ACPI_ERROR((AE_INFO, - "Length in buffer header (%u)(%u) is greater than " - "the physical buffer length (%u) and will overflow", - data_length, buffer_length, - source_desc->buffer.length)); - - return_ACPI_STATUS(AE_AML_BUFFER_LIMIT); - } -#endif - /* Create the transfer/bidirectional/return buffer */ buffer_desc = acpi_ut_create_buffer_object(buffer_length); @@ -342,7 +324,8 @@ acpi_ex_write_serial_bus(union acpi_operand_object *source_desc, /* Copy the input buffer data to the transfer buffer */ buffer = buffer_desc->buffer.pointer; - memcpy(buffer, source_desc->buffer.pointer, data_length); + memcpy(buffer, source_desc->buffer.pointer, + min(buffer_length, source_desc->buffer.length)); /* Lock entire transaction if requested */