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SubjectRe: [PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl()
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On 7/30/21 7:48 PM, Baokun Li wrote:
> 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>
> ---
> drivers/block/nbd.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index c38317979f74..7c838bf8cc31 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1398,6 +1398,8 @@ 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:
> + if (arg && (LLONG_MAX / arg <= config->blksize))
> + return -EINVAL;

Use check_mul_overflow() instead?

--
Jens Axboe

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