linux-kernel - [PATCH AUTOSEL 5.4 04/45] loop: be paranoid on exit and prevent new additions / removals

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Message-Id: <20200810191153.3794446-4-sashal@kernel.org>
Date:   Mon, 10 Aug 2020 15:11:12 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Ming Lei <ming.lei@...hat.com>, Christoph Hellwig <hch@....de>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 04/45] loop: be paranoid on exit and prevent new additions / removals

From: Luis Chamberlain <mcgrof@...nel.org>

[ Upstream commit 200f93377220504c5e56754823e7adfea6037f1a ]

Be pedantic on removal as well and hold the mutex.
This should prevent uses of addition while we exit.

Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/loop.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 565e35e69f249..bddbbf5b3dda2 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2325,6 +2325,8 @@ static void __exit loop_exit(void)
 
 	range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
 
+	mutex_lock(&loop_ctl_mutex);
+
 	idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
 	idr_destroy(&loop_index_idr);
 
@@ -2332,6 +2334,8 @@ static void __exit loop_exit(void)
 	unregister_blkdev(LOOP_MAJOR, "loop");
 
 	misc_deregister(&loop_misc);
+
+	mutex_unlock(&loop_ctl_mutex);
 }
 
 module_init(loop_init);
-- 
2.25.1