From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 4 Sep 2018 17:52:34 +0000 (-0600)
Subject: nbd: don't allow invalid blocksize settings
X-Git-Tag: v4.18.9~148
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56935391aba9292b1b6a30e81c4f42495b3120b7;p=thirdparty%2Fkernel%2Fstable.git

nbd: don't allow invalid blocksize settings

commit bc811f05d77f47059c197a98b6ad242eb03999cb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 3fb95c8d9fd83..15a5ce5bba3da 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -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;