From: Paolo Valente paolo.valente@linaro.org
mainline inclusion from mainline-5.6-rc1 commit ecedd3d7e19911ab8fe42f17b77c0a30fe7f4db3 category: bugfix bugzilla: 50775 CVE: NA
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In bfq_bfqq_move(), the bfq_queue, say Q, to be moved to a new group may happen to be deactivated in the scheduling data structures of the source group (and then activated in the destination group). If Q is referred only by the data structures in the source group when the deactivation happens, then Q is freed upon the deactivation.
This commit addresses this issue by getting an extra reference before the possible deactivation, and releasing this extra reference after Q has been moved.
Tested-by: Chris Evich cevich@redhat.com Tested-by: Oleksandr Natalenko oleksandr@natalenko.name Signed-off-by: Paolo Valente paolo.valente@linaro.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- block/bfq-cgroup.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index ecd3d0ec2f3b..f60089b72691 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -567,6 +567,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_bfqq_expire(bfqd, bfqd->in_service_queue, false, BFQQE_PREEMPTED);
+ /* + * get extra reference to prevent bfqq from being freed in + * next possible deactivate + */ + bfqq->ref++; + if (bfq_bfqq_busy(bfqq)) bfq_deactivate_bfqq(bfqd, bfqq, false, false); else if (entity->on_st) @@ -585,6 +591,8 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
if (!bfqd->in_service_queue && !bfqd->rq_in_driver) bfq_schedule_dispatch(bfqd); + /* release extra ref taken above */ + bfq_put_queue(bfqq); }
/**