On Fri, Nov 1, 2024 at 1:12 AM Maíra Canal <mcanal@xxxxxxxxxx> wrote: > > +cc Kees Cook > > Hi Barry, > > On 31/10/24 09:01, Barry Song wrote: > > On Thu, Oct 31, 2024 at 6:55 PM Maíra Canal <mcanal@xxxxxxxxxx> wrote: > >> > >> Hi Barry, > >> > >> On 30/10/24 20:07, Barry Song wrote: > >>> On Thu, Oct 31, 2024 at 2:03 AM Maíra Canal <mcanal@xxxxxxxxxx> 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@xxxxxxxxxx> > >>>> --- > >>>> 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 > > As `str_dup` is a sized buffer, we don't need to specify the size > parameter. > > > we have checked strlen(str) + 1 > PAGE_SIZE to avoid parsing any pointless > > bootcmd longer than PAGE_SIZE. > > From my point of view, this is an extra layer of safety. A developer > could change `str_dup` to SZ_4K and leave PAGE_SIZE in the check. This > could pass by in a review and we would have a check that allows strings > bigger than the destination buffer in systems using 16KB pages. > > But see that `split_huge_pages_write` uses `strcpy` without any checks. > > I can remove the internal check from `setup_thp_anon` if you feel it > would be more suitable. My point is that we shouldn't remove the strlen(str) + 1 > PAGE_SIZE check, as it could lead to situations like this: For thp_anon=AB, where len(A) = PAGE_SIZE and B is illegal, we would mistakenly interpret the string as valid by ignoring B after trimming it. Therefore, if you remove the check, you could instead do: len = strscpy(str_dup, src); if (len >= sizeof(str_dup)) err; I have no objection to replacing strcpy with strscpy, so feel free to go ahead :-) > > Best Regards, > - Maíra > > > > 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
