Re: [PATCH] ACPICA: Replace strncpy() with strscpy_pad() in acpi_ut_safe_strncpy()

[Jiri Slaby <jirislaby@kernel.org>]

On 29. 05. 26, 9:20, Jiri Slaby wrote:
> On 23. 03. 26, 18:31, Rafael J. Wysocki wrote:
>> On Mon, Mar 23, 2026 at 6:24 PM Kees Cook <kees@kernel.org> wrote:
>>>
>>> Replace the deprecated[1] strncpy() with strscpy_pad() in
>>> acpi_ut_safe_strncpy().
>>>
>>> The function is a "safe strncpy" wrapper that does
>>> strncpy(dest, source, dest_size) followed by manual NUL-termination
>>> at dest[dest_size - 1]. strscpy_pad() is a direct replacement: it
>>> NUL-terminates, zero-pads the remainder, and the manual termination
>>> is no longer needed.
>>>
>>> All callers pass NUL-terminated source strings (C string literals,
>>> __FILE__ via ACPI_MODULE_NAME, or user-provided filenames that have
>>> already been validated). The destinations are fixed-size char arrays
>>> in ACPICA internal structures (allocation->module, aml_op_name,
>>> acpi_gbl_db_debug_filename), all consumed as C strings.
>>>
>>> No behavioral change: strscpy_pad() produces identical output to
>>> strncpy() + manual NUL-termination for NUL-terminated sources that
>>> are shorter than dest_size. For sources longer than dest_size,
>>> strncpy() wrote dest_size non-NUL bytes then the manual termination
>>> overwrote the last byte with NUL; strscpy_pad() writes dest_size-1
>>> bytes plus NUL: same result.
>>>
>>> Link: https://github.com/KSPP/linux/issues/90 [1]
>>> Signed-off-by: Kees Cook <kees@kernel.org>
>>> ---
>>> This touches the ACPICA component shared with the upstream ACPICA
>>> project (https://github.com/acpica/acpica), where the function
>>> is named AcpiUtSafeStrncpy(). The upstream codebase uses its own
>>> platform abstraction layer (acenv.h/acgcc.h) where I've mapped various
>>> kernel APIs before like ACPI_FLEX_ARRAY and similar helpers. However,
>>> acpi_ut_safe_strncpy() is an explicit function implementation rather
>>> than a macro mapping, so the approach for upstreaming this change to
>>> ACPICA is not clear. What's the best way to land this?
>>
>> I can apply this directly, it shouldn't be a major problem for porting
>> patches from the upstream.
> 
> As I reported in https://github.com/acpica/acpica/issues/1158 (but got 
> no reply), this patch breaks build of acpica against 7.1-rc*:
>  > ../../../../../drivers/acpi/acpica/utnonansi.c:171:9: error: implicit 
> declaration of function ‘strscpy_pad’ [-Wimplicit-function-declaration]
> 
> Is strscpy_pad() supposed to be emulated in acpica?

No, I misread the log, it's the in-kernel acpidump failing to build:

~/linux/tools/power/acpi/tools/acpidump> make
   MKDIR    include
   CP       include
   CC       tools/acpidump/apdump.o
   CC       tools/acpidump/apfiles.o
   CC       tools/acpidump/apmain.o
   CC       tools/acpidump/osunixdir.o
   CC       tools/acpidump/osunixmap.o
   CC       tools/acpidump/osunixxf.o
   CC       tools/acpidump/tbprint.o
   CC       tools/acpidump/tbxfroot.o
   CC       tools/acpidump/utascii.o
   CC       tools/acpidump/utbuffer.o
   CC       tools/acpidump/utcksum.o
   CC       tools/acpidump/utdebug.o
   CC       tools/acpidump/utexcep.o
   CC       tools/acpidump/utglobal.o
   CC       tools/acpidump/uthex.o
   CC       tools/acpidump/utmath.o
   CC       tools/acpidump/utnonansi.o
../../../../../drivers/acpi/acpica/utnonansi.c: In function 
‘acpi_ut_safe_strncpy’:
../../../../../drivers/acpi/acpica/utnonansi.c:171:9: error: implicit 
declaration of function ‘strscpy_pad’ [-Wimplicit-function-declaration]
   171 |         strscpy_pad(dest, source, dest_size);
       |         ^~~~~~~~~~~
make: *** [../../Makefile.rules:25: 
/home/xslaby/linux/tools/power/acpi/tools/acpidump/utnonansi.o] Chyba 1

>>> (This is one of the last users of strncpy in the kernel.)
>>> ---
>>>   drivers/acpi/acpica/utnonansi.c | 3 +--
>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/acpi/acpica/utnonansi.c b/drivers/acpi/acpica/ 
>>> utnonansi.c
>>> index ff0802ace19b..3a7952be6545 100644
>>> --- a/drivers/acpi/acpica/utnonansi.c
>>> +++ b/drivers/acpi/acpica/utnonansi.c
>>> @@ -168,8 +168,7 @@ void acpi_ut_safe_strncpy(char *dest, char 
>>> *source, acpi_size dest_size)
>>>   {
>>>          /* Always terminate destination string */
>>>
>>> -       strncpy(dest, source, dest_size);
>>> -       dest[dest_size - 1] = 0;
>>> +       strscpy_pad(dest, source, dest_size);
>>>   }
>>>
>>>   #endif
>>> -- 
>>
> 
> thanks,

-- 
js
suse labs