[PATCH AUTOSEL 6.4 06/15] nbd: Add the maximum limit of allocated index in nbd_dev_add

[Sasha Levin]

From: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>

[ Upstream commit f12bc113ce904777fd6ca003b473b427782b3dde ]

If the index allocated by idr_alloc greater than MINORMASK >> part_shift,
the device number will overflow, resulting in failure to create a block
device.

Fix it by imiting the size of the max allocation.

Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/20230605122159.2134384-1-zhongjinghua@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/block/nbd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 65ecde3e2a5be..6457a094abcc1 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1776,7 +1776,8 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
 		if (err == -ENOSPC)
 			err = -EEXIST;
 	} else {
-		err = idr_alloc(&nbd_index_idr, nbd, 0, 0, GFP_KERNEL);
+		err = idr_alloc(&nbd_index_idr, nbd, 0,
+				(MINORMASK >> part_shift) + 1, GFP_KERNEL);
 		if (err >= 0)
 			index = err;
 	}
-- 
2.39.2