On 4/17/18 5:06 PM, Kees Cook wrote: > On Tue, Apr 17, 2018 at 3:57 PM, Jens Axboe <ax...@kernel.dk> wrote: >> On 4/17/18 3:48 PM, Jens Axboe wrote: >>> On 4/17/18 3:47 PM, Kees Cook wrote: >>>> On Tue, Apr 17, 2018 at 2:39 PM, Jens Axboe <ax...@kernel.dk> wrote: >>>>> On 4/17/18 3:25 PM, Kees Cook wrote: >>>>>> On Tue, Apr 17, 2018 at 1:46 PM, Kees Cook <keesc...@chromium.org> wrote: >>>>>>> I see elv.priv[1] assignments made in a few places -- is it possible >>>>>>> there is some kind of uninitialized-but-not-NULL state that can leak >>>>>>> in there? >>>>>> >>>>>> Got it. This fixes it for me: >>>>>> >>>>>> diff --git a/block/blk-mq.c b/block/blk-mq.c >>>>>> index 0dc9e341c2a7..859df3160303 100644 >>>>>> --- a/block/blk-mq.c >>>>>> +++ b/block/blk-mq.c >>>>>> @@ -363,7 +363,7 @@ static struct request *blk_mq_get_request(struct >>>>>> request_queue *q, >>>>>> >>>>>> rq = blk_mq_rq_ctx_init(data, tag, op); >>>>>> if (!op_is_flush(op)) { >>>>>> - rq->elv.icq = NULL; >>>>>> + memset(&rq->elv, 0, sizeof(rq->elv)); >>>>>> if (e && e->type->ops.mq.prepare_request) { >>>>>> if (e->type->icq_cache && rq_ioc(bio)) >>>>>> blk_mq_sched_assign_ioc(rq, bio); >>>>>> @@ -461,7 +461,7 @@ void blk_mq_free_request(struct request *rq) >>>>>> e->type->ops.mq.finish_request(rq); >>>>>> if (rq->elv.icq) { >>>>>> put_io_context(rq->elv.icq->ioc); >>>>>> - rq->elv.icq = NULL; >>>>>> + memset(&rq->elv, 0, sizeof(rq->elv)); >>>>>> } >>>>>> } >>>>> >>>>> This looks like a BFQ problem, this should not be necessary. Paolo, >>>>> you're calling your own prepare request handler from the insert >>>>> as well, and your prepare request does nothing if rq->elv.icq == NULL. >>>> >>>> I sent the patch anyway, since it's kind of a robustness improvement, >>>> I'd hope. If you fix BFQ also, please add: >>> >>> It's also a memset() in the hot path, would prefer to avoid that... >>> The issue here is really the convoluted bfq usage of insert/prepare, >>> I'm sure Paolo can take it from here. >> >> Does this fix it? >> >> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c >> index f0ecd98509d8..d883469a1582 100644 >> --- a/block/bfq-iosched.c >> +++ b/block/bfq-iosched.c >> @@ -4934,8 +4934,11 @@ static void bfq_prepare_request(struct request *rq, >> struct bio *bio) >> bool new_queue = false; >> bool bfqq_already_existing = false, split = false; >> >> - if (!rq->elv.icq) >> + if (!rq->elv.icq) { >> + rq->elv.priv[0] = rq->elv.priv[1] = NULL; >> return; >> + } >> + >> bic = icq_to_bic(rq->elv.icq); >> >> spin_lock_irq(&bfqd->lock); > > It does! Excellent. :)
Sweet! I'll add a comment and queue it up for 4.17 and mark for stable, with your annotations too. -- Jens Axboe