linux-kernel - [PATCH -next v2] block: fix blktrace debugfs entries leak

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Message-Id: <20230531092606.3037560-2-yukuai1@huaweicloud.com>
Date:   Wed, 31 May 2023 17:26:06 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
        yangerkun@...wei.com
Subject: [PATCH -next v2] block: fix blktrace debugfs entries leak

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

Commit 99d055b4fd4b ("block: remove per-disk debugfs files in
blk_unregister_queue") moves blk_trace_shutdown() from
blk_release_queue() to blk_unregister_queue(), this is safe if blktrace
is created through sysfs, however, there is a regression in corner
case.

blktrace can still be enabled after del_gendisk() through ioctl if
the disk is opened before del_gendisk(), and if blktrace is not shutdown
through ioctl before closing the disk, debugfs entries will be leaked.

Fix this problem by shutdown blktrace in disk_release(), this is safe
because blk_trace_shutdown() is reentrant.

Noted that scsi sg can support blktrace without gendisk and still need
special handling to avoid this problem.

Fixes: 99d055b4fd4b ("block: remove per-disk debugfs files in blk_unregister_queue")
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/genhd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 1cb489b927d5..f5718367965c 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -25,8 +25,9 @@
 #include <linux/pm_runtime.h>
 #include <linux/badblocks.h>
 #include <linux/part_stat.h>
-#include "blk-throttle.h"
+#include <linux/blktrace_api.h>

+#include "blk-throttle.h"
 #include "blk.h"
 #include "blk-mq-sched.h"
 #include "blk-rq-qos.h"
@@ -1171,6 +1172,10 @@ static void disk_release(struct device *dev)
 	might_sleep();
 	WARN_ON_ONCE(disk_live(disk));

+	mutex_lock(&disk->queue->debugfs_mutex);
+	blk_trace_shutdown(disk->queue);
+	mutex_unlock(&disk->queue->debugfs_mutex);
+
 	/*
 	 * To undo the all initialization from blk_mq_init_allocated_queue in
 	 * case of a probe failure where add_disk is never called we have to
-- 
2.39.2