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

From: Sasha Levin
Date: Mon Aug 10 2020 - 15:12:14 EST


From: Luis Chamberlain <mcgrof@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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