2021-08-04 02:05:26

by Baokun Li

Subject: [PATCH -next v3] 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 <[email protected]>
Signed-off-by: Baokun Li <[email protected]>
---
V1->V2:
Use check_mul_overflow().
V2->V3:
The check_mul_overflow function requires the same input parameter type.

drivers/block/nbd.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index c38317979f74..5a42b838d26c 100644
--- 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 +1399,11 @@ 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 (unlikely(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;
--
2.31.1

2021-08-12 02:15:18

by Baokun Li

Subject: Re: [PATCH -next v3] nbd: add the check to prevent overflow in __nbd_ioctl()

?? 2021/8/4 10:12, Baokun Li д??:
> 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 <[email protected]>
> Signed-off-by: Baokun Li <[email protected]>
> ---
> V1->V2:
> Use check_mul_overflow().
> V2->V3:
> The check_mul_overflow function requires the same input parameter type.
>
> drivers/block/nbd.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index c38317979f74..5a42b838d26c 100644
> --- 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 +1399,11 @@ 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 (unlikely(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;

ping

2021-08-13 15:55:34

by Josef Bacik

Subject: Re: [PATCH -next v3] nbd: add the check to prevent overflow in __nbd_ioctl()

On 8/3/21 10:12 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 <[email protected]>
> Signed-off-by: Baokun Li <[email protected]>
> ---
> V1->V2:
> Use check_mul_overflow().
> V2->V3:
> The check_mul_overflow function requires the same input parameter type.
>
> drivers/block/nbd.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index c38317979f74..5a42b838d26c 100644
> --- 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 +1399,11 @@ 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 (unlikely(check_mul_overflow((loff_t)arg,
> + config->blksize,
> + &bytesize)))
> + return -EINVAL;
> + return nbd_set_size(nbd, bytesize, config->blksize);

The unlikely isn't needed here, just makes it harder to read the thing, drop it
and then you can add

Reviewed-by: Josef Bacik <[email protected]>

Thanks,

Josef

2021-08-13 19:11:27

by Jens Axboe

Subject: Re: [PATCH -next v3] nbd: add the check to prevent overflow in __nbd_ioctl()

On 8/3/21 8:12 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.

Applied with unlikely() removed.

--
Jens Axboe