On 2020/8/8 11:42, David Miller wrote:
> From: "luobin (L)" <luob...@huawei.com>
> Date: Sat, 8 Aug 2020 11:36:42 +0800
>
>> On 2020/8/7 17:32, David Laight wrote:
>>>> diff --git a/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
>>>> b/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
>>>> index c6adc776f3c8..1ec88ebf81d6 100644
>>>> --- a/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
>>>> +++ b/drivers/net/ethernet/huawei/hinic/hinic_devlink.c
>>>> @@ -342,9 +342,9 @@ static int chip_fault_show(struct devlink_fmsg *fmsg,
>>>>
>>>> level = event->event.chip.err_level;
>>>> if (level < FAULT_LEVEL_MAX)
>>>> - strncpy(level_str, fault_level[level],
>>>> strlen(fault_level[level]));
>>>> + strncpy(level_str, fault_level[level],
>>>> strlen(fault_level[level]) + 1);
>>>
>>> Have you even considered what that code is actually doing?
> ...
>> I'm sorry that I haven't got what you mean and I haven't found any defects
>> in that code. Can you explain more to me?
>
> David is trying to express the same thing I was trying to explain to
> you, you should use sizeof(level_str) as the third argument because
> the code is trying to make sure that the destination buffer is not
> overrun.
>
> If you use the strlen() of the source buffer, the strncpy() can still
> overflow the destination buffer.
>
> Now do you understand?
> .
>
Thanks for your explanation. I explained that why I didn't use
sizeof(level_str) as the third argument in my previous reply e-mail to you.
Because using sizeof(level_str) as the third argument will still cause the
following compile warning:
In function ‘strncpy’,
inlined from ‘chip_fault_show’ at
drivers/net/ethernet/huawei/hinic/hinic_devlink.c:345:3:
./include/linux/string.h:297:30: warning: ‘__builtin_strncpy’ specified bound
17 equals destination size [-Wstringop-truncation]
297 | #define __underlying_strncpy __builtin_strncpy
Now I know that using strncpy() on NUL-terminated strings is deprecated as Kees
Cook points out and actually there is no need to use it
in my code.
