From a66c38a171ed25488debf80247a9e72e1026e82c Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Tue, 9 May 2017 11:37:27 +0200 Subject: [PATCH] block, bfq: use pointer entity->sched_data only if set In the function __bfq_deactivate_entity, the pointer entity->sched_data could happen to be used before being properly initialized. This led to a NULL pointer dereference. This commit fixes this bug by just using this pointer only where it is safe to do so. Reported-by: Tom Harrison Tested-by: Tom Harrison Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-wf2q.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c index b4fc3e4..8726ede 100644 --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -1114,12 +1114,21 @@ static void bfq_activate_requeue_entity(struct bfq_entity *entity, bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree) { struct bfq_sched_data *sd = entity->sched_data; - struct bfq_service_tree *st = bfq_entity_service_tree(entity); - int is_in_service = entity == sd->in_service_entity; + struct bfq_service_tree *st; + bool is_in_service; if (!entity->on_st) /* entity never activated, or already inactive */ return false; + /* + * If we get here, then entity is active, which implies that + * bfq_group_set_parent has already been invoked for the group + * represented by entity. Therefore, the field + * entity->sched_data has been set, and we can safely use it. + */ + st = bfq_entity_service_tree(entity); + is_in_service = entity == sd->in_service_entity; + if (is_in_service) bfq_calc_finish(entity, entity->service); -- 2.7.4