Re: [PATCH] kni: fix build with gcc 8.1

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 6/20/2018 5:39 PM, Ferruh Yigit wrote:
> On 6/20/2018 12:35 AM, Stephen Hemminger wrote:
>> On Tue, 19 Jun 2018 13:08:55 +0100
>> Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>>
>>> Error observed when CONFIG_RTE_KNI_KMOD_ETHTOOL config option is
>>> enabled.
>>>
>>> build error:
>>> In function ‘strncpy’,
>>>     inlined from ‘igb_get_drvinfo’ at
>>>     .../dpdk/build/build/kernel/linux/kni/igb_ethtool.c:814:2:
>>>     .../include/linux/string.h:246:9: error: ‘__builtin_strncpy’ output
>>>     may be truncated copying 31 bytes from a string of length 42
>>>     [-Werror=stringop-truncation]
>>>       return __builtin_strncpy(p, q, size);
>>>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Fixed by reducing the adapter->fw_version size and adjusting strncpy
>>> limit size.
>>>
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
>>> ---
>>>  kernel/linux/kni/ethtool/igb/igb.h         | 2 +-
>>>  kernel/linux/kni/ethtool/igb/igb_ethtool.c | 2 +-
>>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/kernel/linux/kni/ethtool/igb/igb.h b/kernel/linux/kni/ethtool/igb/igb.h
>>> index 8aa2a3088..5e798ae83 100644
>>> --- a/kernel/linux/kni/ethtool/igb/igb.h
>>> +++ b/kernel/linux/kni/ethtool/igb/igb.h
>>> @@ -592,7 +592,7 @@ struct igb_adapter {
>>>  	int int_mode;
>>>  	u32 rss_queues;
>>>  	u32 vmdq_pools;
>>> -	char fw_version[43];
>>> +	char fw_version[32];
>>
>> Use ETHTOOL_FWVERS_LEN?
> 
> Yes, that is what drvinfo->fw_version uses, and it seems it has been around
> enough to not cause any build issue, will use that one.

Ah so much fun, it has been updated to 43 by me in the past, to prevent another
warning [1] which another part of code has potential to write larger string to
fw_version.

Reducing value back to 32 may bring back that old warning ...

[1]
Fixes: c3698192940c ("kni: fix build with gcc 7.1")

> 
>>
>>>  	u32 wvbr;
>>>  	struct igb_mac_addr *mac_table;
>>>  #ifdef CONFIG_IGB_VMDQ_NETDEV
>>> diff --git a/kernel/linux/kni/ethtool/igb/igb_ethtool.c b/kernel/linux/kni/ethtool/igb/igb_ethtool.c
>>> index 064528bcf..0b8b25ff1 100644
>>> --- a/kernel/linux/kni/ethtool/igb/igb_ethtool.c
>>> +++ b/kernel/linux/kni/ethtool/igb/igb_ethtool.c
>>> @@ -812,7 +812,7 @@ static void igb_get_drvinfo(struct net_device *netdev,
>>>  	strncpy(drvinfo->version, igb_driver_version, sizeof(drvinfo->version) - 1);
>>>  
>>>  	strncpy(drvinfo->fw_version, adapter->fw_version,
>>> -		sizeof(drvinfo->fw_version) - 1);
>>> +		sizeof(drvinfo->fw_version));
>>
>> Why not:
>> 	strlcpy(drvinfo->fw_version, adapter->fw_version,
>> 		sizeof(drvinfo->fw_version));
> 
> Just to be cautious about changing API, to not have any problem with older
> version of kernels.
> But it seems strlcpy supported long enough to not cause an issue, I will use it.
>