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Sat, 31 Jul 2021 07:57:47 -0700 (PDT) Subject: Re: [PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl() To: Baokun Li , josef@toxicpanda.com, linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org Cc: patchwork@huawei.com, Hulk Robot References: <20210731014854.3953274-1-libaokun1@huawei.com> From: Jens Axboe Message-ID: 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 List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 > Signed-off-by: Baokun Li > --- > 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