linux-kernel - Re: [PATCH v3 4/4] mm: huge_memory: Use strscpy() instead of strcpy()

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Message-ID: <b31bd54c-400c-4432-8b4b-0ba12bcf8011@igalia.com>
Date: Thu, 31 Oct 2024 07:55:42 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Barry Song <baohua@...nel.org>
Cc: Jonathan Corbet <corbet@....net>,
 Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>,
 David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Lance Yang
 <ioworker0@...il.com>, linux-mm@...ck.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel-dev@...lia.com
Subject: Re: [PATCH v3 4/4] mm: huge_memory: Use strscpy() instead of strcpy()

Hi Barry,

On 30/10/24 20:07, Barry Song wrote:
> On Thu, Oct 31, 2024 at 2:03 AM Maíra Canal <mcanal@...lia.com> wrote:
>>
>> Replace strcpy() with strscpy() in mm/huge_memory.c
>>
>> strcpy() has been deprecated because it is generally unsafe, so help to
>> eliminate it from the kernel source.
>>
>> Link: https://github.com/KSPP/linux/issues/88
>> Signed-off-by: Maíra Canal <mcanal@...lia.com>
>> ---
>>   mm/huge_memory.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index f92068864469..8f41a694433c 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -989,7 +989,7 @@ static int __init setup_thp_anon(char *str)
>>
>>          if (!str || strlen(str) + 1 > PAGE_SIZE)
>>                  goto err;
>> -       strcpy(str_dup, str);
>> +       strscpy(str_dup, str);
> 
> What is the difference between strcpy and strscpy without a size parameter?
> 
> we have already a check and goto err. strcpy() is entirely safe.
>           if (!str || strlen(str) + 1 > PAGE_SIZE)
>                   goto err;
> 
> My understanding is that we don't need this patch.

strcpy() is a deprecated interface [1]. From the GitHub issue I linked
in the commit description, Kees states: "A lot of kernel code is still
using strcpy(). While the CONFIG_FORTIFY_SOURCE wrapper macros tend to
make its use mostly safe, it would be nice to eliminate the function
from the kernel entirely."

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy

Best Regards,
- Maíra

> 
>>
>>          always = huge_anon_orders_always;
>>          madvise = huge_anon_orders_madvise;
>> @@ -4175,7 +4175,7 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
>>
>>                  tok = strsep(&buf, ",");
>>                  if (tok) {
>> -                       strcpy(file_path, tok);
>> +                       strscpy(file_path, tok);
>>                  } else {
>>                          ret = -EINVAL;
>>                          goto out;
>> --
>> 2.46.2
>>
> 
> Thanks
> barry