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SubjectRe: [PATCH net-next v1] hinic: fix strncpy output truncated compile warnings
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On 2020/8/8 20:50, David Laight wrote:
> From: luobin (L)
>> Sent: 08 August 2020 04:37
>>
>> On 2020/8/7 17:32, David Laight wrote:
>>> From: Luo bin
>>>> Sent: 07 August 2020 03:09
>>>>
>>>> fix the compile warnings of 'strncpy' output truncated before
>>>> terminating nul copying N bytes from a string of the same length
>>>>
>>>> Signed-off-by: Luo bin <luobin9@huawei.com>
>>>> Reported-by: kernel test robot <lkp@intel.com>
>>>> ---
>>>> V0~V1:
>>>> - use the strlen()+1 pattern consistently
>>>>
>>>> drivers/net/ethernet/huawei/hinic/hinic_devlink.c | 8 ++++----
>>>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> 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?
>>>
>>> David
>>
>> 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?
>
> If you can't see it you probably shouldn't be submitting patches....
>
> Consider what happens when the string is long.
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>
Thanks for your explanation and review. The fault_level[level] is a fixed and NUL-terminated character
string in that code and its length is smaller than the dest buffer size so I think using
strlen(fault_level[level]) + 1 will not overflow the destination buffer. But using strncpy() on
NUL-terminated strings is dangerous indeed and there is totally no need to use it in that code
as Kees points out.

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