Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: usercopy whitelist woe in scsi_sense_cache
To:     Kees Cook <keescook@chromium.org>
Cc:     Paolo Valente <paolo.valente@linaro.org>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Bart Van Assche <bart.vanassche@wdc.com>,
        David Windsor <dave@nullcore.net>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Hannes Reinecke <hare@suse.com>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        linux-block@vger.kernel.org
References: <10360653.ov98egbaqx@natalenko.name>
 <2864697.7uzmEJovl2@natalenko.name>
 <CAGXu5jLSmJv9AstzsgSscrv-wA7FwfrxAKRxj-FVBmihQvnj1g@mail.gmail.com>
 <CAGXu5j+dh1zm32iBjRVh0s+3gLJYgjwt+z1aBJmrK2Cr8XPWnA@mail.gmail.com>
 <CAGXu5jLhnWnUiscP9B=kTEFNyRw9jgFn7Zr5FxhZrO20553+1Q@mail.gmail.com>
 <CAGXu5jKuZwicyyXH2gB3vp-OjtS+MkG+hqxV1cq1jaG9vAAO=g@mail.gmail.com>
 <CAGXu5jLQuzpjFcfjpT=MvgOxBizFNMjnfmY+E7eCHkDAV5swHg@mail.gmail.com>
 <CAGXu5jJTMqbXia7TmN2yEW11SM+XC3pkMt=bb+xBrY7-OOf=tw@mail.gmail.com>
 <CAGXu5j+xX3kDDS_sPY44hPVb=8isMX-evYzPx3ur=rge1rL5JQ@mail.gmail.com>
 <CAGXu5jJmvKcANUSsCz3fjGSv-tv1hceNd3rOpT4WTfYRb65RRA@mail.gmail.com>
 <8473f909-2123-0cfc-43b1-beba0b1aef9b@kernel.dk>
 <CAGXu5jL9miO3OXpjAxm9t8v=f_f5StB=Tk=aV8BVRdEj-Y-PDA@mail.gmail.com>
 <CAGXu5jKVPQi0cdTbe5Y1DNHdiJ6-kEFRBTNv7znuqT9w5eifGg@mail.gmail.com>
 <07f263ff-cea6-ac3c-944b-0f36fee8ba25@kernel.dk>
 <CAGXu5j+kHipvoyFWjGp8M6+83zbd6yHOzwxQ-2LNBQbD5-jS9w@mail.gmail.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <8b32e079-d4e6-3fea-a89d-ff856e4e13b1@kernel.dk>
Date:   Tue, 17 Apr 2018 15:48:19 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.0
MIME-Version: 1.0
In-Reply-To: <CAGXu5j+kHipvoyFWjGp8M6+83zbd6yHOzwxQ-2LNBQbD5-jS9w@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 4/17/18 3:47 PM, Kees Cook wrote:
> On Tue, Apr 17, 2018 at 2:39 PM, Jens Axboe <axboe@kernel.dk> wrote:
>> On 4/17/18 3:25 PM, Kees Cook wrote:
>>> On Tue, Apr 17, 2018 at 1:46 PM, Kees Cook <keescook@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.

-- 
Jens Axboe