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SubjectRe: [PATCH V2] auxdisplay: use correct string length
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On 2018/2/12 20:53, Miguel Ojeda wrote:
> On Tue, Jan 16, 2018 at 10:38 AM, Xiongfeng Wang
> <wangxiongfeng2@huawei.com> wrote:
>> From: Xiongfeng Wang <xiongfeng.wang@linaro.org>
>>
>> gcc-8 reports
>>
>> drivers/auxdisplay/panel.c: In function 'panel_attach':
>> ./include/linux/string.h:245:9: warning: '__builtin_strncpy' specified
>> bound 12 equals destination size [-Wstringop-truncation]
>>
>> We need one less byte or call strlcpy() to make it a nul-terminated
>> string.
>>
>> Signed-off-by: Xiongfeng Wang <xiongfeng.wang@linaro.org>
>> ---
>> drivers/auxdisplay/panel.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c
>> index ea7869c..d288900 100644
>> --- a/drivers/auxdisplay/panel.c
>> +++ b/drivers/auxdisplay/panel.c
>> @@ -1506,10 +1506,10 @@ static struct logical_input *panel_bind_key(const char *name, const char *press,
>> key->rise_time = 1;
>> key->fall_time = 1;
>>
>> - strncpy(key->u.kbd.press_str, press, sizeof(key->u.kbd.press_str));
>> - strncpy(key->u.kbd.repeat_str, repeat, sizeof(key->u.kbd.repeat_str));
>> + strncpy(key->u.kbd.press_str, press, sizeof(key->u.kbd.press_str) - 1);
>> + strncpy(key->u.kbd.repeat_str, repeat, sizeof(key->u.kbd.repeat_str) - 1);
>> strncpy(key->u.kbd.release_str, release,
>> - sizeof(key->u.kbd.release_str));
>> + sizeof(key->u.kbd.release_str) - 1);
>
> Are you sure about this patch? `kbd` says "strings can be non null-terminated".
>
> Willy, maybe those should just be memcpy()s? (unless the remaining
> bytes, if any, must be 0).
Sorry, my apologies. I think I made a mistake. I meant to use strlcpy(), but this
also decrease the destination storage size by one.
I think, if the strings can be non null-terminated, we can just use memcpy().
This may suppress the gcc warning.

Thanks,
Xiongfeng

>
> Thanks,
> Miguel
>
>> list_add(&key->list, &logical_inputs);
>> return key;
>> }
>> --
>> 1.8.3.1
>>
>
> .
>

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