linux-kernel - [PATCH] drivers/block/null_blk/main: Fix a double free in null

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Message-Id: <20210426143229.7374-1-lyl2019@mail.ustc.edu.cn>
Date:   Mon, 26 Apr 2021 07:32:29 -0700
From:   Lv Yunlong <lyl2019@...l.ustc.edu.cn>
To:     axboe@...nel.dk, damien.lemoal@....com, johannes.thumshirn@....com,
        martin.petersen@...cle.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Subject: [PATCH] drivers/block/null_blk/main: Fix a double free in null_init.

In null_init, null_add_dev(dev) is called.
In null_add_dev, it calls null_free_zoned_dev(dev) to free dev->zones
via kvfree(dev->zones) in out_cleanup_zone branch and returns err.
Then null_init accept the err code and then calls null_free_dev(dev).

But in null_free_dev(dev), dev->zones is freed again by
null_free_zoned_dev().

My patch set dev->zones to NULL in null_free_zoned_dev() after
kvfree(dev->zones) is called, to avoid the double free.

Fixes: 2984c8684f962 ("nullb: factor disk parameters")
Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
---
 drivers/block/null_blk/zoned.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
index bfcab1c782b5..dae54dd1aeac 100644
--- a/drivers/block/null_blk/zoned.c
+++ b/drivers/block/null_blk/zoned.c
@@ -180,6 +180,7 @@ int null_register_zoned_dev(struct nullb *nullb)
 void null_free_zoned_dev(struct nullb_device *dev)
 {
 	kvfree(dev->zones);
+	dev->zones = NULL;
 }
 
 int null_report_zones(struct gendisk *disk, sector_t sector,
-- 
2.25.1