linux-kernel - Re: [PATCH 2/2] livepatch: Use correct kobject cleanup function

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]

Date:   Tue, 30 Apr 2019 17:08:11 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     "Tobin C. Harding" <tobin@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] livepatch: Use correct kobject cleanup function

On Tue 2019-04-30 10:15:34, Tobin C. Harding wrote:
> The correct cleanup function after a call to kobject_init_and_add() has
> succeeded is kobject_del() _not_ kobject_put().  kobject_del() calls
> kobject_put().

Really? I see only kobject_put(kobj->parent) in kobject_del.
It decreases a reference of the _parent_ object and not
the given one.

Also the section "Kobject removal" in Documentation/kobject.txt
says that kobject_del() is for two-stage removal. kobject_put()
still needs to get called at a later time.

IMHO, this patch causes that kobject_put() would never get called.

That said, we could probably make the removal a bit cleaner
by using kobject_del() in klp_free_patch_start() and
kobject_put() in klp_free_patch_finish(). But I have
to think more about it.

Best Regards,
Petr