[ Upstream commit eed47d19d9362bdd958e4ab56af480b9dbf6b2b6 ]
The function bfq_bfqq_expire() invokes the function __bfq_bfqq_expire(), and the latter may free the in-service bfq-queue. If this happens, then no other instruction of bfq_bfqq_expire() must be executed, or a use-after-free will occur.
Basing on the assumption that __bfq_bfqq_expire() invokes bfq_put_queue() on the in-service bfq-queue exactly once, the queue is assumed to be freed if its refcounter is equal to one right before invoking __bfq_bfqq_expire().
But, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") this assumption is false. __bfq_bfqq_expire() may also invoke bfq_weights_tree_remove() and, since commit 9dee8b3b057e ("block, bfq: fix queue removal from weights tree"), also the latter function may invoke bfq_put_queue(). So __bfq_bfqq_expire() may invoke bfq_put_queue() twice, and this is the actual case where the in-service queue may happen to be freed.
To address this issue, this commit moves the check on the refcounter of the queue right around the last bfq_put_queue() that may be invoked on the queue.
Fixes: 9dee8b3b057e ("block, bfq: fix queue removal from weights tree") Reported-by: Dmitrii Tcvetkov demfloro@demfloro.ru Reported-by: Douglas Anderson dianders@chromium.org Tested-by: Dmitrii Tcvetkov demfloro@demfloro.ru Tested-by: Douglas Anderson dianders@chromium.org Signed-off-by: Paolo Valente paolo.valente@linaro.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/bfq-iosched.c | 15 +++++++-------- block/bfq-iosched.h | 2 +- block/bfq-wf2q.c | 17 +++++++++++++++-- 3 files changed, 23 insertions(+), 11 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index e5ed28629271..72510c470001 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2804,7 +2804,7 @@ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) bfq_remove_request(q, rq); }
-static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) +static bool __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) { /* * If this bfqq is shared between multiple processes, check @@ -2837,9 +2837,11 @@ static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) /* * All in-service entities must have been properly deactivated * or requeued before executing the next function, which - * resets all in-service entites as no more in service. + * resets all in-service entities as no more in service. This + * may cause bfqq to be freed. If this happens, the next + * function returns true. */ - __bfq_bfqd_reset_in_service(bfqd); + return __bfq_bfqd_reset_in_service(bfqd); }
/** @@ -3244,7 +3246,6 @@ void bfq_bfqq_expire(struct bfq_data *bfqd, bool slow; unsigned long delta = 0; struct bfq_entity *entity = &bfqq->entity; - int ref;
/* * Check whether the process is slow (see bfq_bfqq_is_slow). @@ -3313,10 +3314,8 @@ void bfq_bfqq_expire(struct bfq_data *bfqd, * reason. */ __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); - ref = bfqq->ref; - __bfq_bfqq_expire(bfqd, bfqq); - - if (ref == 1) /* bfqq is gone, no more actions on it */ + if (__bfq_bfqq_expire(bfqd, bfqq)) + /* bfqq is gone, no more actions on it */ return;
bfqq->injected_service = 0; diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 746bd570b85a..ca98c98a8179 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -993,7 +993,7 @@ bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree); bool next_queue_may_preempt(struct bfq_data *bfqd); struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd); -void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd); +bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd); void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, bool ins_into_idle_tree, bool expiration); void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c index 4aab1a8191f0..8077bf71d2ac 100644 --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -1599,7 +1599,8 @@ struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) return bfqq; }
-void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) +/* returns true if the in-service queue gets freed */ +bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) { struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; @@ -1623,8 +1624,20 @@ void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) * service tree either, then release the service reference to * the queue it represents (taken with bfq_get_entity). */ - if (!in_serv_entity->on_st) + if (!in_serv_entity->on_st) { + /* + * If no process is referencing in_serv_bfqq any + * longer, then the service reference may be the only + * reference to the queue. If this is the case, then + * bfqq gets freed here. + */ + int ref = in_serv_bfqq->ref; bfq_put_queue(in_serv_bfqq); + if (ref == 1) + return true; + } + + return false; }
void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,