Hi,
在 2023/11/03 18:13, Li Lingfeng 写道:
From: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
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.
Do you mean that nbd_open concurrent with nbd_dev_remove?
nbd_open nbd_dev_remove
del_gendisk
kfree(nbd)
mutex_lock
nbd = disk->private_data
-> UAF
refcount_inc_not_zero
Looks like it's possible, but you should use READ/WRITE_ONCE() here,
because disk->pravate_data can be accessed concurrently.
Thanks,
Kuai
Fixes: 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and blk_cleanup_disk")
Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
---
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);
