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Date:   Tue, 8 Nov 2022 08:48:47 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Gerd Bayer <gbayer@linux.ibm.com>
Cc:     Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Niklas Schnelle <schnelle@linux.ibm.com>,
        linux-kernel@vger.kernel.org, linux-next@vger.kernel.org,
        linux-nvme@lists.infradead.org
Subject: Re: nvme-pci: NULL pointer dereference in nvme_dev_disable() on
 linux-next
Message-ID: <20221108074846.GA22674@lst.de>
References: <fad4d2d5e24eabe1a4fcab75c5d080a6229dc88b.camel@linux.ibm.com>
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Below is the minimal fix.  I'll see if I sort out the mess that is
probe/reset failure vs ->remove a bit better, though.

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f94b05c585cbc..577bacdcfee08 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -5160,6 +5160,8 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
 
 void nvme_stop_queues(struct nvme_ctrl *ctrl)
 {
+	if (!ctrl->tagset)
+		return;
 	if (!test_and_set_bit(NVME_CTRL_STOPPED, &ctrl->flags))
 		blk_mq_quiesce_tagset(ctrl->tagset);
 	else
@@ -5169,6 +5171,8 @@ EXPORT_SYMBOL_GPL(nvme_stop_queues);
 
 void nvme_start_queues(struct nvme_ctrl *ctrl)
 {
+	if (!ctrl->tagset)
+		return;
 	if (test_and_clear_bit(NVME_CTRL_STOPPED, &ctrl->flags))
 		blk_mq_unquiesce_tagset(ctrl->tagset);
 }