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| author |   Paolo Valente <paolo.valente@linaro.org> | 2020-03-21 10:45:18 +0100 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2020-03-21 14:30:58 -0600 |
| commit | fd1bb3ae54a9a2e0c42709de861c69aa146b8955 (patch) | |
| tree | 865016ef8439e74c8e2e427ce471adc140950968 /block | |
| parent | block, bfq: fix use-after-free in bfq_idle_slice_timer_body (diff) | |
| download | wireguard-linux-fd1bb3ae54a9a2e0c42709de861c69aa146b8955.tar.xz wireguard-linux-fd1bb3ae54a9a2e0c42709de861c69aa146b8955.zip | |
block, bfq: move forward the getting of an extra ref in bfq_bfqq_move
Commit ecedd3d7e199 ("block, bfq: get extra ref to prevent a queue
from being freed during a group move") gets an extra reference to a
bfq_queue before possibly deactivating it (temporarily), in
bfq_bfqq_move(). This prevents the bfq_queue from disappearing before
being reactivated in its new group.
Yet, the bfq_queue may also be expired (i.e., its service may be
stopped) before the bfq_queue is deactivated. And also an expiration
may lead to a premature freeing. This commit fixes this issue by
simply moving forward the getting of the extra reference already
introduced by commit ecedd3d7e199 ("block, bfq: get extra ref to
prevent a queue from being freed during a group move").
Reported-by: cki-project@redhat.com
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/bfq-cgroup.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index f0ff6654af28..9d963ed518d1 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -642,6 +642,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, { struct bfq_entity *entity = &bfqq->entity; + /* + * Get extra reference to prevent bfqq from being freed in + * next possible expire or deactivate. + */ + bfqq->ref++; + /* If bfqq is empty, then bfq_bfqq_expire also invokes * bfq_del_bfqq_busy, thereby removing bfqq and its entity * from data structures related to current group. Otherwise we @@ -652,12 +658,6 @@ 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_or_in_serv) @@ -677,7 +677,7 @@ 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 */ + /* release extra ref taken above, bfqq may happen to be freed now */ bfq_put_queue(bfqq); } |