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Date: Sun, 9 Aug 2020 11:35:50 +0800 From: "luobin (L)" <luobin9@...wei.com> To: David Laight <David.Laight@...LAB.COM>, "davem@...emloft.net" <davem@...emloft.net> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "luoxianjun@...wei.com" <luoxianjun@...wei.com>, "yin.yinshi@...wei.com" <yin.yinshi@...wei.com>, "cloud.wangxiaoyun@...wei.com" <cloud.wangxiaoyun@...wei.com>, "chiqijun@...wei.com" <chiqijun@...wei.com> Subject: Re: [PATCH net-next v1] hinic: fix strncpy output truncated compile warnings 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@...wei.com> >>>> Reported-by: kernel test robot <lkp@...el.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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