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

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Date:   Wed, 23 Aug 2023 08:14:19 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Heiko Carstens <hca@...ux.ibm.com>
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 8/23/23 8:13 AM, Heiko Carstens 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?

Yep will drop it for now.

-- 
Jens Axboe