linux-kernel - [PATCH v4 1/2] scsi: sg: fix blktrace debugfs entries leakage

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Date:   Fri,  9 Jun 2023 16:39:12 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, axboe@...nel.dk, dgilbert@...erlog.com,
        jejb@...ux.ibm.com, martin.petersen@...cle.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, yukuai3@...wei.com,
        yukuai1@...weicloud.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: [PATCH v4 1/2] scsi: sg: fix blktrace debugfs entries leakage

From: Yu Kuai <yukuai3@...wei.com>

sg_ioctl() support to enable blktrace, which will create debugfs entries
"/sys/kernel/debug/block/sgx/", however, there is no guarantee that user
will remove these entries through ioctl, and deleting sg device doesn't
cleanup these blktrace entries.

This problem can be fixed by cleanup blktrace while releasing
request_queue, however, it's not a good idea to do this special handling
in common layer just for sg device.

Fix this problem by shutdown bltkrace in sg_device_destroy(), where the
device is deleted and all the users close the device, also grab a
scsi_device reference from sg_add_device() to prevent scsi_device to be
freed before sg_device_destroy();

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 drivers/scsi/sg.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 037f8c98a6d3..dd62c5b0d079 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1496,6 +1496,10 @@ sg_add_device(struct device *cl_dev)
 	int error;
 	unsigned long iflags;
 
+	error = scsi_device_get(scsidp);
+	if (error)
+		return error;
+
 	error = -ENOMEM;
 	cdev = cdev_alloc();
 	if (!cdev) {
@@ -1553,6 +1557,7 @@ sg_add_device(struct device *cl_dev)
 out:
 	if (cdev)
 		cdev_del(cdev);
+	scsi_device_put(scsidp);
 	return error;
 }
 
@@ -1560,6 +1565,7 @@ static void
 sg_device_destroy(struct kref *kref)
 {
 	struct sg_device *sdp = container_of(kref, struct sg_device, d_ref);
+	struct request_queue *q = sdp->device->request_queue;
 	unsigned long flags;
 
 	/* CAUTION!  Note that the device can still be found via idr_find()
@@ -1567,6 +1573,11 @@ sg_device_destroy(struct kref *kref)
 	 * any other cleanup.
 	 */
 
+	mutex_lock(&q->debugfs_mutex);
+	blk_trace_shutdown(q);
+	mutex_unlock(&q->debugfs_mutex);
+	scsi_device_put(sdp->device);
+
 	write_lock_irqsave(&sg_index_lock, flags);
 	idr_remove(&sg_index_idr, sdp->index);
 	write_unlock_irqrestore(&sg_index_lock, flags);
-- 
2.39.2