Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH -next] nbd: add the check to prevent overflow in
 __nbd_ioctl()
To:     Baokun Li <libaokun1@huawei.com>, josef@toxicpanda.com,
        linux-block@vger.kernel.org, nbd@other.debian.org,
        linux-kernel@vger.kernel.org
Cc:     patchwork@huawei.com, Hulk Robot <hulkci@huawei.com>
References: <20210731014854.3953274-1-libaokun1@huawei.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <b2582b8f-7cb8-f936-2d78-4d8b5feb0c12@kernel.dk>
Date:   Sat, 31 Jul 2021 08:57:44 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20210731014854.3953274-1-libaokun1@huawei.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

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