linux-kernel - Re: [PATCH] partitions/ibm: refactor deprecated strncpy

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Message-ID: <D14D69B0-63E4-4650-A7F0-44F6CF81F9F9@kernel.org>
Date:   Wed, 23 Aug 2023 07:22:29 -0700
From:   Kees Cook <kees@...nel.org>
To:     Heiko Carstens <hca@...ux.ibm.com>, Jens Axboe <axboe@...nel.dk>
CC:     Justin Stitt <justinstitt@...gle.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Stefan Haberland <sth@...ux.ibm.com>,
        Jan Hoeppner <hoeppner@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        Viktor Mihajlovski <mihajlov@...ux.ibm.com>
Subject: Re: [PATCH] partitions/ibm: refactor deprecated strncpy

On August 23, 2023 7:13:04 AM PDT, Heiko Carstens <hca@...ux.ibm.com> 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@...r.kernel.org
>> > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
>> > ---
>> >  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