nbd: add the check to prevent overflow in __nbd_ioctl()

hulk inclusion
category: bugfix
bugzilla: 175174
CVE: NA

-------------------------------------------------

If user specify a large enough value of NBD blocks option, it may trigger
signed integer overflow which may lead to nbd->config->bytesize becomes a
large or small value, zero in particular.

UBSAN: Undefined behaviour in drivers/block/nbd.c:325:31
signed integer overflow:
1024 * 4611686155866341414 cannot be represented in type 'long long int'
[...]
Call trace:
[...]
 handle_overflow+0x188/0x1dc lib/ubsan.c:192
 __ubsan_handle_mul_overflow+0x34/0x44 lib/ubsan.c:213
 nbd_size_set drivers/block/nbd.c:325 [inline]
 __nbd_ioctl drivers/block/nbd.c:1342 [inline]
 nbd_ioctl+0x998/0xa10 drivers/block/nbd.c:1395
 __blkdev_driver_ioctl block/ioctl.c:311 [inline]
[...]

Although it is not a big deal, still silence the UBSAN by limit
the input value.
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NBaokun Li <libaokun1@huawei.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210804021212.990223-1-libaokun1@huawei.com
[axboe: dropped unlikely()]
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Conflicts:
	drivers/block/nbd.c
Signed-off-by: NBaokun Li <libaokun1@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/block/nbd.c

@@ -1317,6 +1317,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		       unsigned int cmd, unsigned long arg)
 {
 	struct nbd_config *config = nbd->config;
+	loff_t bytesize;
 
 	switch (cmd) {
 	case NBD_DISCONNECT:
@@ -1339,6 +1340,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 			     div_s64(arg, config->blksize));
 		return 0;
 	case NBD_SET_SIZE_BLOCKS:
+		if (check_mul_overflow((loff_t)arg, config->blksize, &bytesize))
+			return -EINVAL;
 		nbd_size_set(nbd, config->blksize, arg);
 		return 0;
 	case NBD_SET_TIMEOUT: