linux-kernel - Re: [PATCH linux-next] parisc: use strscpy() to instead of strncpy()

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Date:   Tue, 27 Dec 2022 22:38:04 +0100
From:   Helge Deller <deller@....de>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        yang.yang29@....com.cn
Cc:     linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        xu.panda@....com.cn
Subject: Re: [PATCH linux-next] parisc: use strscpy() to instead of strncpy()

Hi James,

On 12/27/22 13:38, James Bottomley wrote:
> On Fri, 2022-12-23 at 08:55 +0100, Helge Deller wrote:
>> On 12/23/22 03:40, yang.yang29@....com.cn wrote:
>>> From: Xu Panda <xu.panda@....com.cn>
>>>
>>> The implementation of strscpy() is more robust and safer.
>>> That's now the recommended way to copy NUL-terminated strings.
>>
>> Thanks for your patch, but....
>>
>>> Signed-off-by: Xu Panda <xu.panda@....com.cn>
>>> Signed-off-by: Yang Yang <yang.yang29@....com>
>>> ---
>>>    drivers/parisc/pdc_stable.c | 9 +++------
>>>    1 file changed, 3 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/parisc/pdc_stable.c
>>> b/drivers/parisc/pdc_stable.c
>>> index d6af5726ddf3..403bca0021c5 100644
>>> --- a/drivers/parisc/pdc_stable.c
>>> +++ b/drivers/parisc/pdc_stable.c
>>> @@ -274,8 +274,7 @@ pdcspath_hwpath_write(struct pdcspath_entry
>>> *entry, const char *buf, size_t coun
>>>
>>>          /* We'll use a local copy of buf */
>>>          count = min_t(size_t, count, sizeof(in)-1);
>>> -       strncpy(in, buf, count);
>>> -       in[count] = '\0';
>>> +       strscpy(in, buf, count + 1);
>>
>> could you resend it somewhat simplified, e.g.
>> strscpy(in, buf, sizeof(in));
>
> I don't think you can: count is the size of buf, if that's < sizeof(in)
> you've introduced a write beyond end of buffer.  In fact sysfs tends to
> pass pages as buffers, so there's no actual problem, but if that ever
> changed ...

Huh?... he doesn't change "count", so what's wrong with the latest patch?

Helge