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

[Barry Song <21cnbao@gmail.com>]

On Thu, Oct 31, 2024 at 6:55 PM Maíra Canal <mcanal@igalia.com> wrote:
>
> Hi Barry,
>
> On 30/10/24 20:07, Barry Song wrote:
> > On Thu, Oct 31, 2024 at 2:03 AM Maíra Canal <mcanal@igalia.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@igalia.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."

I don't see any value added here since strscpy() has no size parameter and
we have checked strlen(str) + 1 > PAGE_SIZE to avoid parsing any pointless
bootcmd longer than PAGE_SIZE.

But I have no objection to this patch if other people like it.

>
> [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