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Subject[PATCH] ACPI: EC: Reference count query handlers under lock
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

There is a race condition in acpi_ec_get_query_handler()
theoretically allowing query handlers to go away before
reference 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>
---
drivers/acpi/ec.c | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)

Index: linux-pm/drivers/acpi/ec.c
===================================================================
--- linux-pm.orig/drivers/acpi/ec.c
+++ linux-pm/drivers/acpi/ec.c
@@ -1053,28 +1053,20 @@ 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)


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