linux-kernel - [PATCH AUTOSEL 6.4 09/15] scsi: sg: fix blktrace debugfs entries leakage

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Message-Id: <20230702194020.1776895-9-sashal@kernel.org>
Date:   Sun,  2 Jul 2023 15:40:14 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yu Kuai <yukuai3@...wei.com>, Christoph Hellwig <hch@....de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        dgilbert@...erlog.com, jejb@...ux.ibm.com,
        linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 6.4 09/15] scsi: sg: fix blktrace debugfs entries leakage

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

[ Upstream commit db59133e927916d8a25ee1fd8264f2808040909d ]

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>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Martin K. Petersen <martin.petersen@...cle.com>
Link: https://lore.kernel.org/r/20230610022003.2557284-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/sg.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 037f8c98a6d36..0adfbd77437f3 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 +1573,9 @@ sg_device_destroy(struct kref *kref)
 	 * any other cleanup.
 	 */
 
+	blk_trace_remove(q);
+	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