linux-kernel - [PATCH v4 5/5] loop: be paranoid on exit and prevent new additions / removals

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Message-Id: <20200509031058.8239-6-mcgrof@kernel.org>
Date:   Sat,  9 May 2020 03:10:58 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     axboe@...nel.dk, viro@...iv.linux.org.uk, bvanassche@....org,
        gregkh@...uxfoundation.org, rostedt@...dmis.org, mingo@...hat.com,
        jack@...e.cz, ming.lei@...hat.com, nstange@...e.de,
        akpm@...ux-foundation.org
Cc:     mhocko@...e.com, yukuai3@...wei.com, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH v4 5/5] loop: be paranoid on exit and prevent new additions / removals

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

I cannot trigger an issue with this though, this is
just a fix done through code inspection.

Reviewed-by: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Luis Chamberlain <mcgrof@...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 14372df0f354..54fbcbd930de 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2333,6 +2333,8 @@ 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);
 
@@ -2340,6 +2342,8 @@ 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