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

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: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210804021212.990223-1-libaokun1@huawei.com
[axboe: dropped unlikely()]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c383179..f822648 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1384,6 +1384,7 @@ 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:
@@ -1398,8 +1399,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
        case NBD_SET_SIZE:
                return nbd_set_size(nbd, arg, config->blksize);
        case NBD_SET_SIZE_BLOCKS:
-               return nbd_set_size(nbd, arg * config->blksize,
-                                   config->blksize);
+               if (check_mul_overflow((loff_t)arg, config->blksize, &bytesize))
+                       return -EINVAL;
+               return nbd_set_size(nbd, bytesize, config->blksize);
        case NBD_SET_TIMEOUT:
                nbd_set_cmd_timeout(nbd, arg);
                return 0;