Commit bc811f05 authored Sep 04, 2018 by Jens Axboe

nbd: don't allow invalid blocksize settings



syzbot reports a divide-by-zero off the NBD_SET_BLKSIZE ioctl.
We need proper validation of the input here. Not just if it's
zero, but also if the value is a power-of-2 and in a valid
range. Add that.

Cc: stable@vger.kernel.org
Reported-by: syzbot <syzbot+25dbecbec1e62c6b0dd4@syzkaller.appspotmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 31118850

drivers/block/nbd.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1239,6 +1239,9 @@ static int __nbd_ioctl(struct block_device bdev, struct nbd_device nbd,
		case NBD_SET_SOCK:
		return nbd_add_socket(nbd, arg, false);
		case NBD_SET_BLKSIZE:
		if (!arg \|\| !is_power_of_2(arg) \|\| arg < 512 \|\|
		arg > PAGE_SIZE)
		return -EINVAL;
		nbd_size_set(nbd, arg,
		div_s64(config->bytesize, arg));
		return 0;