acpi: bus: check once more for an empty list after locking it

upstream commit: f0a37e008750ead1751b7d5e89d220a260a46147

List could have become empty after the unlocked check that was made earlier,
so check again inside the lock.

Should fix https://bugzilla.redhat.com/show_bug.cgi?id=427765

Signed-off-by: Chuck Ebbert <cebbert@redhat.com>
Cc: <stable@kernel.org>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index f4487c38d9f294893ebc460f5f05c27b3918b77d..3401e2cfd3ab08d62d5a200e0ce38a6d4ccacee4 100644 (file)
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -350,10 +350,11 @@ int acpi_bus_receive_event(struct acpi_bus_event *event)
        }
 
        spin_lock_irqsave(&acpi_bus_event_lock, flags);
-       entry =
-           list_entry(acpi_bus_event_list.next, struct acpi_bus_event, node);
-       if (entry)
+       if (!list_empty(&acpi_bus_event_list)) {
+               entry = list_entry(acpi_bus_event_list.next,
+                                  struct acpi_bus_event, node);
                list_del(&entry->node);
+       }
        spin_unlock_irqrestore(&acpi_bus_event_lock, flags);
 
        if (!entry)