[PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl()

[PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl()

[Baokun Li]

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;
 		return nbd_set_size(nbd, arg * config->blksize,
 				    config->blksize);
 	case NBD_SET_TIMEOUT:
-- 
2.31.1

Re: [PATCH -next] nbd: add the check to prevent overflow in __nbd_ioctl()

[Jens Axboe]

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