Re: [PATCH] partitions/ibm: refactor deprecated strncpy

[Kees Cook]

On August 23, 2023 7:13:04 AM PDT, Heiko Carstens <hca@xxxxxxxxxxxxx> wrote:
>On Wed, Aug 23, 2023 at 03:49:36PM +0200, Heiko Carstens wrote:
>> On Tue, Aug 22, 2023 at 11:59:26PM +0000, Justin Stitt wrote:
>> > `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>> > 
>> > A suitable replacement is `strscpy` [2] due to the fact that it
>> > guarantees NUL-termination on its destination buffer argument which is
>> > _not_ the case for `strncpy`!
>> > 
>> > Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
>> > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
>> > Link: https://github.com/KSPP/linux/issues/90
>> > Cc: linux-hardening@xxxxxxxxxxxxxxx
>> > Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
>> > ---
>> >  block/partitions/ibm.c | 8 ++++----
>> >  1 file changed, 4 insertions(+), 4 deletions(-)
>> > 
>> > diff --git a/block/partitions/ibm.c b/block/partitions/ibm.c
>> > index 403756dbd50d..e5893cf71b57 100644
>> > --- a/block/partitions/ibm.c
>> > +++ b/block/partitions/ibm.c
>> > @@ -111,11 +111,11 @@ static int find_label(struct parsed_partitions *state,
>> >  		    !strcmp(temp, "LNX1") ||
>> >  		    !strcmp(temp, "CMS1")) {
>> >  			if (!strcmp(temp, "VOL1")) {
>> > -				strncpy(type, label->vol.vollbl, 4);
>> > -				strncpy(name, label->vol.volid, 6);
>> > +				strscpy(type, label->vol.vollbl, 4);
>> > +				strscpy(name, label->vol.volid, 6);
>> >  			} else {
>> > -				strncpy(type, label->lnx.vollbl, 4);
>> > -				strncpy(name, label->lnx.volid, 6);
>> > +				strscpy(type, label->lnx.vollbl, 4);
>> > +				strscpy(name, label->lnx.volid, 6);
>> >  			}
>> >  			EBCASC(type, 4);
>> >  			EBCASC(name, 6);
>> 
>> I'm quite sure this is not correct, since both type and name are not
>> necessarily NUL-terminated, and this code operates on purpose on such
>> strings.
>> 
>> Since currently Stefan and Jan are both not available, I added Peter
>> Oberparleiter to Cc who hopefully knows better than me.
>
>I was just made aware of that this patch is already in linux-next. And
>indeed: partition detection does not work anymore for DASDs. With this
>patch reverted it works again.
>
>Jens, can you remove or revert this patch again, please?


Looks like this should be strtomem_pad() rather than strscpy()...


-- 
Kees Cook