This is a note to let you know that I've just added the patch titled nbd: fix possible overflow for 'first_minor' in nbd_dev_add() to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: nbd-fix-possible-overflow-for-first_minor-in-nbd_dev.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 89b8f8377e576ef57c82df1c6ab458f8f2e59538 Author: Yu Kuai <yukuai3@xxxxxxxxxx> Date: Tue Nov 2 09:52:35 2021 +0800 nbd: fix possible overflow for 'first_minor' in nbd_dev_add() [ 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@xxxxxxxxxx> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20211102015237.2309763-3-yebin10@xxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 0d820c4dec176..577c7dba5d78d 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1749,11 +1749,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) 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; }