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ACPI: EC: Reference count query handlers under lock

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There is a race condition in acpi_ec_get_query_handler()
theoretically allowing query handlers to go away before refernce
counting them.

In order to avoid it, call kref_get() on query handlers under
ec->mutex.

Also simplify the code a bit while at it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2019-12-27 11:04:21 +01:00
parent 46cf053efe
commit 3df663a147
1 changed files with 4 additions and 12 deletions
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16
drivers/acpi/ec.c
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@ -1052,29 +1052,21 @@ void acpi_ec_unblock_transactions(void)
/* --------------------------------------------------------------------------
Event Management
-------------------------------------------------------------------------- */
static struct acpi_ec_query_handler *
acpi_ec_get_query_handler(struct acpi_ec_query_handler *handler)
{
if (handler)
kref_get(&handler->kref);
return handler;
}
static struct acpi_ec_query_handler *
acpi_ec_get_query_handler_by_value(struct acpi_ec *ec, u8 value)
{
struct acpi_ec_query_handler *handler;
bool found = false;
mutex_lock(&ec->mutex);
list_for_each_entry(handler, &ec->list, node) {
if (value == handler->query_bit) {
found = true;
break;
kref_get(&handler->kref);
mutex_unlock(&ec->mutex);
return handler;
}
}
mutex_unlock(&ec->mutex);
return found ? acpi_ec_get_query_handler(handler) : NULL;
return NULL;
}
static void acpi_ec_query_handler_release(struct kref *kref)