From 6f1637795f2827d36aec9e0246487f5852e8abf7 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Mon, 25 Oct 2021 10:54:23 +0800
Subject: [PATCH] zram: fix race between zram_reset_device() and
 disksize_store()
Git-commit: 6f1637795f2827d36aec9e0246487f5852e8abf7
Reviewed-by: Luis Chamberlain <mcgrof@suse.com>
Patch-mainline: v5.16-rc1
References: bsc#1170269

When the ->init_lock is released in zram_reset_device(), disksize_store()
can come in and try to allocate meta, but zram_reset_device() is freeing
free meta, so cause races.

Link: https://lore.kernel.org/linux-block/20210927163805.808907-1-mcgrof@kernel.org/T/#mc617f865a3fa2778e40f317ddf48f6447c20c073
Reported-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Link: https://lore.kernel.org/r/20211025025426.2815424-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/block/zram/zram_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f09259f..313e093 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1691,12 +1691,13 @@ static void zram_reset_device(struct zram *zram)
 	set_capacity(zram->disk, 0);
 	part_stat_set_all(&zram->disk->part0, 0);
 
-	up_write(&zram->init_lock);
 	/* I/O operation under all of CPU are done so let's free */
 	zram_meta_free(zram, disksize);
 	memset(&zram->stats, 0, sizeof(zram->stats));
 	zcomp_destroy(comp);
 	reset_bdev(zram);
+
+	up_write(&zram->init_lock);
 }
 
 static ssize_t disksize_store(struct device *dev,