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From:   Kees Cook <keescook@chromium.org>
Date:   Tue, 17 Apr 2018 14:25:25 -0700
Message-ID: <CAGXu5jKVPQi0cdTbe5Y1DNHdiJ6-kEFRBTNv7znuqT9w5eifGg@mail.gmail.com>
Subject: Re: usercopy whitelist woe in scsi_sense_cache
To:     Jens Axboe <axboe@kernel.dk>,
        Paolo Valente <paolo.valente@linaro.org>
Cc:     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
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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));
                }
        }


-- 
Kees Cook
Pixel Security