linux-kernel - [PATCH V3 3/4] zram: avoid race between zram_remove and disksize

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Message-Id: <20211025025426.2815424-4-ming.lei@redhat.com>
Date:   Mon, 25 Oct 2021 10:54:25 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, Luis Chamberlain <mcgrof@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V3 3/4] zram: avoid race between zram_remove and disksize_store

After resetting device in zram_remove(), disksize_store still may come and
allocate resources again before deleting gendisk, fix the race by resetting
zram after del_gendisk() returns. At that time, disksize_store can't come
any more.

Reported-by: Luis Chamberlain <mcgrof@...nel.org>
Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 drivers/block/zram/zram_drv.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8883de7aa3d7..dba93b8ce511 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2002,6 +2002,13 @@ static int zram_remove(struct zram *zram)
 	/* del_gendisk drains pending reset_store */
 	WARN_ON_ONCE(claimed && zram->claim);
 
+	/*
+	 * disksize_store() may be called in between zram_reset_device()
+	 * and del_gendisk(), so run the last reset to avoid leaking
+	 * anything allocated with disksize_store()
+	 */
+	zram_reset_device(zram);
+
 	blk_cleanup_disk(zram->disk);
 	kfree(zram);
 	return 0;
-- 
2.31.1