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From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: "axboe@kernel.dk" <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>
Subject: Re: [REPORT] BUG: KASAN: use-after-free in bt_iter+0x80/0xf8
Date: Wed, 19 Aug 2020 16:58:43 +0800	[thread overview]
Message-ID: <20200819085843.GA2730150@T590> (raw)
In-Reply-To: <585bb054-2009-4abc-f1e8-802e494ba49b@huawei.com>

On Wed, Aug 19, 2020 at 08:43:46AM +0100, John Garry wrote:
> On 19/08/2020 01:00, Ming Lei wrote:
> > On Tue, Aug 18, 2020 at 07:19:57PM +0100, John Garry wrote:
> > > On 18/08/2020 13:03, John Garry wrote:
> > > > Hi guys,
> > > > 
> > > > JFYI, While doing some testing on v5.9-rc1, I stumbled across this:
> > > 
> > > I bisected to here (hopefully without mistake):
> > 
> > This one is a long-term problem, see the following discussion:
> > 
> > https://lore.kernel.org/linux-block/1553492318-1810-1-git-send-email-jianchao.w.wang@oracle.com/
> > 
> > 
> 
> ah, right. I vaguely remember this. Well, if we didn't have a reliable
> reproducer before, we do now.

OK, that is great, please try the following patch:

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 32d82e23b095..f18632c524e9 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -185,19 +185,19 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 {
 	struct bt_iter_data *iter_data = data;
 	struct blk_mq_hw_ctx *hctx = iter_data->hctx;
-	struct blk_mq_tags *tags = hctx->tags;
+	struct blk_mq_tags *tags = hctx->sched_tags ?: hctx->tags;
 	bool reserved = iter_data->reserved;
 	struct request *rq;
 
 	if (!reserved)
 		bitnr += tags->nr_reserved_tags;
-	rq = tags->rqs[bitnr];
+	rq = tags->static_rqs[bitnr];
 
 	/*
 	 * We can hit rq == NULL here, because the tagging functions
 	 * test and set the bit before assigning ->rqs[].
 	 */
-	if (rq && rq->q == hctx->queue)
+	if (rq && rq->tag >= 0 && rq->q == hctx->queue)
 		return iter_data->fn(hctx, rq, iter_data->data, reserved);
 	return true;
 }
@@ -406,7 +406,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 		return;
 
 	queue_for_each_hw_ctx(q, hctx, i) {
-		struct blk_mq_tags *tags = hctx->tags;
+		struct blk_mq_tags *tags = hctx->sched_tags ?: hctx->tags;
 
 		/*
 		 * If no software queues are currently mapped to this

-- 
Ming


  reply	other threads:[~2020-08-19  8:59 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-18 12:03 [REPORT] BUG: KASAN: use-after-free in bt_iter+0x80/0xf8 John Garry
2020-08-18 18:19 ` John Garry
2020-08-19  0:00   ` Ming Lei
2020-08-19  7:43     ` John Garry
2020-08-19  8:58       ` Ming Lei [this message]
2020-08-19 10:14         ` John Garry
2020-08-19 14:21           ` Ming Lei
2020-08-19 16:48             ` John Garry

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