[v3] mm: add more kernel parameters to control mTHP

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

Posted by Maíra Canal 3 weeks, 4 days ago

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);
 
 	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

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

Posted by Lance Yang 3 weeks, 4 days ago

Hi Maíra,

Looks like a lot of kernel code is still using strcpy() ;p

On Wed, Oct 30, 2024 at 9:03 PM 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>

Feel free to add:
Reviewed-by: Lance Yang <ioworker0@gmail.com>

Thanks,
Lance


> ---
>  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);
>
>         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
>

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

Posted by Barry Song 3 weeks, 4 days ago

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.

>
>         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

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

Posted by Maíra Canal 3 weeks, 3 days ago

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."

[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

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

Posted by Barry Song 3 weeks, 3 days ago

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

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

Posted by Maíra Canal 3 weeks, 3 days ago

+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@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

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.

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

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

Posted by Barry Song 3 weeks, 3 days ago

On Fri, Nov 1, 2024 at 1:12 AM Maíra Canal <mcanal@igalia.com> 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@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
>
> 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

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

Posted by Barry Song 3 weeks, 3 days ago

On Fri, Nov 1, 2024 at 9:27 AM Barry Song <21cnbao@gmail.com> wrote:
>
> On Fri, Nov 1, 2024 at 1:12 AM Maíra Canal <mcanal@igalia.com> 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@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
> >
> > 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;

Perhaps -E2BIG ( or < 0) i'm not quite sure :-)

>
> 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