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);
--
Jens Axboe
