Commit c27f3d01 authored by Hans de Goede's avatar Hans de Goede Committed by Rafael J. Wysocki

ACPICA: Fix race in generic_serial_bus (I2C) and GPIO op_region parameter handling

ACPICA commit c9e0116952363b0fa815143dca7e9a2eb4fefa61

The handling of the generic_serial_bus (I2C) and GPIO op_regions in
acpi_ev_address_space_dispatch() passes a number of extra parameters
to the address-space handler through the address-space Context pointer
(instead of using more function parameters).

The Context is shared between threads, so if multiple threads try to
call the handler for the same address-space at the same time, then
a second thread could change the parameters of a first thread while
the handler is running for the first thread.

An example of this race hitting is the Lenovo Yoga Tablet2 1015L,
where there are both attrib_bytes accesses and attrib_byte accesses
to the same address-space. The attrib_bytes access stores the number
of bytes to transfer in Context->access_length. Where as for the
attrib_byte access the number of bytes to transfer is always 1 and
field_obj->Field.access_length is unused (so 0). Both types of
accesses racing from different threads leads to the following problem:

 1. Thread a. starts an attrib_bytes access, stores a non 0 value
    from field_obj->Field.access_length in Context->access_length

 2. Thread b. starts an attrib_byte access, stores 0 in
    Context->access_length

 3. Thread a. calls i2c_acpi_space_handler() (under Linux). Which
    sees that the access-type is ACPI_GSB_ACCESS_ATTRIB_MULTIBYTE
    and calls acpi_gsb_i2c_read_bytes(..., Context->access_length)

 4. At this point Context->access_length is 0 (set by thread b.)

rather then the field_obj->Field.access_length value from thread a.
This 0 length reads leads to the following errors being logged:

 i2c i2c-0: adapter quirk: no zero length (addr 0x0078, size 0, read)
 i2c i2c-0: i2c read 0 bytes from client@0x78 starting at reg 0x0 failed, error: -95

Note this is just an example of the problems which this race can cause.

There are likely many more (sporadic) problems caused by this race.

This commit adds a new context_mutex to struct acpi_object_addr_handler
and makes acpi_ev_address_space_dispatch() take that mutex when
using the shared Context to pass extra parameters to an address-space
handler, fixing this race.

Note the new mutex must be taken *after* exiting the interpreter,
therefor the existing acpi_ex_exit_interpreter() call is moved to above
the code which stores the extra parameters in the Context.

Link: https://github.com/acpica/acpica/commit/c9e01169Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarBob Moore <robert.moore@intel.com>
Signed-off-by: default avatarErik Kaneda <erik.kaneda@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 938bdd1d
......@@ -284,6 +284,7 @@ struct acpi_object_addr_handler {
acpi_adr_space_handler handler;
struct acpi_namespace_node *node; /* Parent device */
void *context;
acpi_mutex context_mutex;
acpi_adr_space_setup setup;
union acpi_operand_object *region_list; /* Regions using this handler */
union acpi_operand_object *next;
......
......@@ -489,6 +489,13 @@ acpi_ev_install_space_handler(struct acpi_namespace_node *node,
/* Init handler obj */
status =
acpi_os_create_mutex(&handler_obj->address_space.context_mutex);
if (ACPI_FAILURE(status)) {
acpi_ut_remove_reference(handler_obj);
goto unlock_and_exit;
}
handler_obj->address_space.space_id = (u8)space_id;
handler_obj->address_space.handler_flags = flags;
handler_obj->address_space.region_list = NULL;
......
......@@ -112,6 +112,8 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
union acpi_operand_object *region_obj2;
void *region_context = NULL;
struct acpi_connection_info *context;
acpi_mutex context_mutex;
u8 context_locked;
acpi_physical_address address;
ACPI_FUNCTION_TRACE(ev_address_space_dispatch);
......@@ -136,6 +138,8 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
}
context = handler_desc->address_space.context;
context_mutex = handler_desc->address_space.context_mutex;
context_locked = FALSE;
/*
* It may be the case that the region has never been initialized.
......@@ -204,6 +208,23 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
handler = handler_desc->address_space.handler;
address = (region_obj->region.address + region_offset);
ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
"Handler %p (@%p) Address %8.8X%8.8X [%s]\n",
&region_obj->region.handler->address_space, handler,
ACPI_FORMAT_UINT64(address),
acpi_ut_get_region_name(region_obj->region.
space_id)));
if (!(handler_desc->address_space.handler_flags &
ACPI_ADDR_HANDLER_DEFAULT_INSTALLED)) {
/*
* For handlers other than the default (supplied) handlers, we must
* exit the interpreter because the handler *might* block -- we don't
* know what it will do, so we can't hold the lock on the interpreter.
*/
acpi_ex_exit_interpreter();
}
/*
* Special handling for generic_serial_bus and general_purpose_io:
* There are three extra parameters that must be passed to the
......@@ -212,6 +233,11 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
* 2) Length of the above buffer
* 3) Actual access length from the access_as() op
*
* Since we pass these extra parameters via the context, which is
* shared between threads, we must lock the context to avoid these
* parameters being changed from another thread before the handler
* has completed running.
*
* In addition, for general_purpose_io, the Address and bit_width fields
* are defined as follows:
* 1) Address is the pin number index of the field (bit offset from
......@@ -221,6 +247,14 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
if ((region_obj->region.space_id == ACPI_ADR_SPACE_GSBUS) &&
context && field_obj) {
status =
acpi_os_acquire_mutex(context_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
goto re_enter_interpreter;
}
context_locked = TRUE;
/* Get the Connection (resource_template) buffer */
context->connection = field_obj->field.resource_buffer;
......@@ -230,6 +264,14 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
if ((region_obj->region.space_id == ACPI_ADR_SPACE_GPIO) &&
context && field_obj) {
status =
acpi_os_acquire_mutex(context_mutex, ACPI_WAIT_FOREVER);
if (ACPI_FAILURE(status)) {
goto re_enter_interpreter;
}
context_locked = TRUE;
/* Get the Connection (resource_template) buffer */
context->connection = field_obj->field.resource_buffer;
......@@ -239,28 +281,15 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
bit_width = field_obj->field.bit_length;
}
ACPI_DEBUG_PRINT((ACPI_DB_OPREGION,
"Handler %p (@%p) Address %8.8X%8.8X [%s]\n",
&region_obj->region.handler->address_space, handler,
ACPI_FORMAT_UINT64(address),
acpi_ut_get_region_name(region_obj->region.
space_id)));
if (!(handler_desc->address_space.handler_flags &
ACPI_ADDR_HANDLER_DEFAULT_INSTALLED)) {
/*
* For handlers other than the default (supplied) handlers, we must
* exit the interpreter because the handler *might* block -- we don't
* know what it will do, so we can't hold the lock on the interpreter.
*/
acpi_ex_exit_interpreter();
}
/* Call the handler */
status = handler(function, address, bit_width, value, context,
region_obj2->extra.region_context);
if (context_locked) {
acpi_os_release_mutex(context_mutex);
}
if (ACPI_FAILURE(status)) {
ACPI_EXCEPTION((AE_INFO, status, "Returned by Handler for [%s]",
acpi_ut_get_region_name(region_obj->region.
......@@ -277,6 +306,7 @@ acpi_ev_address_space_dispatch(union acpi_operand_object *region_obj,
}
}
re_enter_interpreter:
if (!(handler_desc->address_space.handler_flags &
ACPI_ADDR_HANDLER_DEFAULT_INSTALLED)) {
/*
......
......@@ -201,6 +201,8 @@ acpi_remove_address_space_handler(acpi_handle device,
/* Now we can delete the handler object */
acpi_os_release_mutex(handler_obj->address_space.
context_mutex);
acpi_ut_remove_reference(handler_obj);
goto unlock_and_exit;
}
......
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