[PATCH 5.14 718/849] nbd: fix possible overflow for first_minor in nbd_dev_add()

Greg Kroah-Hartman
2021-11-15T23:19:13Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 940c264984fd1457918393c49674f6b39ee16506 ]

If 'part_shift' is not zero, then 'index << part_shift' might
overflow to a value that is not greater than '0xfffff', then sysfs
might complains about duplicate creation.

Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20211102015237.2309763-3-yebin10@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/nbd.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index bdc6d656e785c..f72ff515ee51b 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1777,11 +1777,11 @@ static int nbd_dev_add(int index)
disk->major = NBD_MAJOR;

/* Too big first_minor can cause duplicate creation of
- * sysfs files/links, since MKDEV() expect that the max bits of
- * first_minor is 20.
+ * sysfs files/links, since index << part_shift might overflow, or
+ * MKDEV() expect that the max bits of first_minor is 20.
*/
disk->first_minor = index << part_shift;
- if (disk->first_minor > MINORMASK) {
+ if (disk->first_minor < index || disk->first_minor > MINORMASK) {
err = -EINVAL;
goto out_free_idr;
}
--
2.33.0