2021-09-28 20:23:50

by Gustavo A. R. Silva

Subject: [PATCH][net-next] net/mlx4: Use array_size() helper in copy_to_user()

Use array_size() helper instead of the open-coded version in
copy_to_user(). These sorts of multiplication factors need
to be wrapped in array_size().

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index f7053a74e6a8..4d4f9cf9facb 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
@@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
buf += PAGE_SIZE;
}
} else {
- err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
+ err = copy_to_user((void __user *)buf, init_ents,
+ array_size(entries, cqe_size)) ?
-EFAULT : 0;
}

--
2.27.0

2021-09-29 10:26:19

by Tariq Toukan

Subject: Re: [PATCH][net-next] net/mlx4: Use array_size() helper in copy_to_user()

On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:
> Use array_size() helper instead of the open-coded version in
> copy_to_user(). These sorts of multiplication factors need
> to be wrapped in array_size().
>
> Link: https://github.com/KSPP/linux/issues/160
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
> index f7053a74e6a8..4d4f9cf9facb 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/cq.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
> @@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
> buf += PAGE_SIZE;
> }
> } else {
> - err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
> + err = copy_to_user((void __user *)buf, init_ents,
> + array_size(entries, cqe_size)) ?
> -EFAULT : 0;
> }
>
>

Thanks for your patch.
Reviewed-by: Tariq Toukan <[email protected]>

2021-09-29 17:55:10

by Eric Dumazet

Subject: Re: [PATCH][net-next] net/mlx4: Use array_size() helper in copy_to_user()

On 9/29/21 3:24 AM, Tariq Toukan wrote:
>
>
> On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:
>> Use array_size() helper instead of the open-coded version in
>> copy_to_user(). These sorts of multiplication factors need
>> to be wrapped in array_size().
>>
>> Link: https://github.com/KSPP/linux/issues/160
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>> ---
>>   drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
>> index f7053a74e6a8..4d4f9cf9facb 100644
>> --- a/drivers/net/ethernet/mellanox/mlx4/cq.c
>> +++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
>> @@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
>>               buf += PAGE_SIZE;
>>           }
>>       } else {
>> -        err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
>> +        err = copy_to_user((void __user *)buf, init_ents,
>> +                   array_size(entries, cqe_size)) ?
>>               -EFAULT : 0;
>>       }
>>  
>
> Thanks for your patch.
> Reviewed-by: Tariq Toukan <[email protected]>

Not sure why avoiding size_t overflows would make this code safer.
init_ents contains PAGE_SIZE bytes...

BTW

Is @entries guaranteed to be a power of two ?

This function seems to either copy one chunk ( <= PAGE_SIZE),
or a number of full pages.

2021-09-29 19:29:27

by Tariq Toukan

Subject: Re: [PATCH][net-next] net/mlx4: Use array_size() helper in copy_to_user()

On 9/29/2021 8:21 PM, Eric Dumazet wrote:
>
>
> On 9/29/21 3:24 AM, Tariq Toukan wrote:
>>
>>
>> On 9/28/2021 11:17 PM, Gustavo A. R. Silva wrote:
>>> Use array_size() helper instead of the open-coded version in
>>> copy_to_user(). These sorts of multiplication factors need
>>> to be wrapped in array_size().
>>>
>>> Link: https://github.com/KSPP/linux/issues/160
>>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>>> ---
>>>   drivers/net/ethernet/mellanox/mlx4/cq.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
>>> index f7053a74e6a8..4d4f9cf9facb 100644
>>> --- a/drivers/net/ethernet/mellanox/mlx4/cq.c
>>> +++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
>>> @@ -314,7 +314,8 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
>>>               buf += PAGE_SIZE;
>>>           }
>>>       } else {
>>> -        err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
>>> +        err = copy_to_user((void __user *)buf, init_ents,
>>> +                   array_size(entries, cqe_size)) ?
>>>               -EFAULT : 0;
>>>       }
>>>
>>
>> Thanks for your patch.
>> Reviewed-by: Tariq Toukan <[email protected]>
>
> Not sure why avoiding size_t overflows would make this code safer.
> init_ents contains PAGE_SIZE bytes...
>
> BTW
>
> Is @entries guaranteed to be a power of two ?

Yes.

>
> This function seems to either copy one chunk ( <= PAGE_SIZE),
> or a number of full pages.
>

Exactly. No remainder handling is needed, for the reason you mentioned
above.