[PATCH AUTOSEL 5.10 25/47] ACPICA: Fix race in generic_serial_bus (I2C) and GPIO op_region parameter handling

Sasha Levin
2021-03-02T12:54:33Z

From: Hans de Goede <hdegoede@redhat.com>

[ Upstream commit c27f3d011b08540e68233cf56274fdc34bebb9b5 ]

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/c9e01169
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/acpica/acobject.h | 1 +
drivers/acpi/acpica/evhandler.c | 7 ++++
drivers/acpi/acpica/evregion.c | 64 ++++++++++++++++++++++++---------
drivers/acpi/acpica/evxfregn.c | 2 ++
4 files changed, 57 insertions(+), 17 deletions(-)

diff --git a/drivers/acpi/acpica/acobject.h b/drivers/acpi/acpica/acobject.h
index 9f0219a8cb98..dd7efafcb103 100644
--- a/drivers/acpi/acpica/acobject.h
+++ b/drivers/acpi/acpica/acobject.h
@@ -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;
diff --git a/drivers/acpi/acpica/evhandler.c b/drivers/acpi/acpica/evhandler.c
index 5884eba047f7..3438dc187efb 100644
--- a/drivers/acpi/acpica/evhandler.c
+++ b/drivers/acpi/acpica/evhandler.c
@@ -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;
diff --git a/drivers/acpi/acpica/evregion.c b/drivers/acpi/acpica/evregion.c
index 738d4b231f34..980efc9bd5ee 100644
--- a/drivers/acpi/acpica/evregion.c
+++ b/drivers/acpi/acpica/evregion.c
@@ -111,6 +111,8 @@ 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);
@@ -135,6 +137,8 @@ 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.
@@ -203,6 +207,23 @@ 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
@@ -211,6 +232,11 @@ 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
@@ -220,6 +246,14 @@ 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;
@@ -229,6 +263,14 @@ 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;
@@ -238,28 +280,15 @@ 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.
@@ -276,6 +305,7 @@ 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)) {
/*
diff --git a/drivers/acpi/acpica/evxfregn.c b/drivers/acpi/acpica/evxfregn.c
index da97fd0c6b51..3bb06f17a18b 100644
--- a/drivers/acpi/acpica/evxfregn.c
+++ b/drivers/acpi/acpica/evxfregn.c
@@ -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;
}
--
2.30.1