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

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Message-ID: <20230823141304.14378-F-hca@linux.ibm.com>
Date:   Wed, 23 Aug 2023 16:13:04 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     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 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?