linux-kernel - Re: block-rbd: One function call less in rbd_dev_probe

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOi1vP_MoqiPqNMGJVEeAyBywtkHbZrn7cLayEgdT1cL63c7KQ@mail.gmail.com>
Date:	Tue, 24 Nov 2015 22:54:17 +0100
From:	Ilya Dryomov <idryomov@...il.com>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:	Alex Elder <elder@...nel.org>, Sage Weil <sage@...hat.com>,
	Ceph Development <ceph-devel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: block-rbd: One function call less in rbd_dev_probe_parent() after
 error detection

On Tue, Nov 24, 2015 at 9:34 PM, SF Markus Elfring
<elfring@...rs.sourceforge.net> wrote:
>> Well, there isn't any _literal_ linking (e.g. adding to a link list,
>> etc) in this case.  We just bump some refs and do probe to fill in the
>> newly allocated parent.
>
> Thanks for your clarification.
>
>
>> The actual linking (rbd_dev->parent = parent) is done right before
>> returning so we never have to undo it in rbd_dev_probe_parent() and
>> that's the only reason your patch probably doesn't break anything.
>
> Is this function implementation just also affected by an issue
> which is mentioned in the Linux document "CodingStyle" as "one err bugs"?

No, why?  "one err bug" as per CodingStyle is a NULL deref on line 2 if
foo is NULL.  If it was just "err: kfree(foo); return ret;", a NULL foo
would be perfectly OK.

1       err:
2               kfree(foo->bar);
3               kfree(foo);
4               return ret;

If you can spot such a NULL deref in rbd_dev_probe_parent(), I'd gladly
take a patch.

>
>
>> Think about what happens if, after your patch is applied, someone moves
>> that assignment up or adds an extra step that can fail after it...
>
> Is such a software maintenance concern really enough to delay (or reject)
> my second update suggestion in this small patch series?

Yes - it's rejected because it messes up the order of cleanup for no
good reason.  I realize why you think the patch is correct and it's not
without merit, but it just doesn't fit the weird rbd_dev_probe_parent()
contract.

Thanks,

                Ilya
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/