linux-kernel - Re: [PATCH] params: Replace deprecated strcpy() with strscpy()

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Message-Id: <47F53A47-D331-4DC5-8146-7ED09C65177F@linux.dev>
Date: Wed, 13 Aug 2025 14:15:50 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
 Shyam Saini <shyamsaini@...ux.microsoft.com>,
 Luis Chamberlain <mcgrof@...nel.org>,
 Dmitry Antipov <dmantipov@...dex.ru>,
 linux-kernel@...r.kernel.org,
 linux-modules@...r.kernel.org
Subject: Re: [PATCH] params: Replace deprecated strcpy() with strscpy()

On 13. Aug 2025, at 13:42, Petr Pavlu wrote:
> On 8/13/25 11:33 AM, Thorsten Blum wrote:
>> On 13. Aug 2025, at 10:59, Petr Pavlu wrote:
>>> Since the code already calculated the length of val and that it fits
>>> into kps->string, is there any advantage (or disadvantage) to using
>>> strscpy() over memcpy()?
>> 
>> strscpy() guarantees that the destination buffer 'kps->string' is always
>> NUL-terminated, even if the source 'val' is not. memcpy() just copies
>> the bytes as they are.
>> 
>> If it were guaranteed that 'val' is always NUL-terminated, memcpy()
>> would be fine too, but since param_set_copystring() is exported, we
>> probably can't make that assumption.
> 
> The function param_set_copystring() checks using
> 'strnlen(val, kps->maxlen) == kps->maxlen' if val contains NUL in the
> first kps->maxlen bytes. It can use memcpy() instead of strscpy() to
> avoid repeating this work.

I see, and yes

	memcpy(kps->string, val, len + 1);

would then be slightly more efficient because strscpy() would just
recompute the length before calling memcpy() internally.

I'll submit a v2.

Thanks,
Thorsten