zram: avoid race between zram_remove and disksize_store

mainline inclusion
from mainline-v5.16-rc1
commit 5a4b6536
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I674BF
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5a4b653655d554b5f51a5d2252882708c56a6f7e

--------------------------------

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: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Link: https://lore.kernel.org/r/20211025025426.2815424-4-ming.lei@redhat.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Conflicts:
	drivers/block/zram/zram_drv.c
Signed-off-by: NLonglong Xia <xialonglong1@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/block/zram/zram_drv.c

@@ -2023,6 +2023,13 @@ 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_queue(zram->disk->queue);
 	put_disk(zram->disk);
 	kfree(zram);