linux-kernel - [PATCH] nbd: fix uaf in nbd

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Date:   Fri,  3 Nov 2023 18:13:34 +0800
From:   Li Lingfeng <lilingfeng@...weicloud.com>
To:     josef@...icpanda.com
Cc:     linux-kernel@...r.kernel.org, hch@....de,
        linux-block@...r.kernel.org, nbd@...er.debian.org, axboe@...nel.dk,
        chaitanya.kulkarni@....com, yukuai1@...weicloud.com,
        houtao1@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com,
        lilingfeng@...weicloud.com, lilingfeng3@...wei.com
Subject: [PATCH] nbd: fix uaf in nbd_open

From: Li Lingfeng <lilingfeng3@...wei.com>

Commit 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and
blk_cleanup_disk") cleans up disk by blk_cleanup_disk() and it won't set
disk->private_data as NULL as before. UAF may be triggered in nbd_open()
if someone tries to open nbd device right after nbd_put() since refcount
of nbd device is zero and private_data is not NULL.

Fixes: 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and blk_cleanup_disk")
Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
---
 drivers/block/nbd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 800f131222fc..aab93b836e84 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -250,6 +250,7 @@ static void nbd_dev_remove(struct nbd_device *nbd)
 	struct gendisk *disk = nbd->disk;
 
 	del_gendisk(disk);
+	disk->private_data = NULL;
 	put_disk(disk);
 	blk_mq_free_tag_set(&nbd->tag_set);
 
-- 
2.31.1