linux-kernel - Re: [PATCHv3 2/3] kernel: add support for live patching

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: <alpine.LNX.2.00.1411211637020.27891@pobox.suse.cz>
Date:	Fri, 21 Nov 2014 16:46:32 +0100 (CET)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Jiri Kosina <jkosina@...e.cz>, Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Petr Mladek <pmladek@...e.cz>,
	Christoph Hellwig <hch@...radead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	live-patching@...r.kernel.org, x86@...nel.org, kpatch@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 2/3] kernel: add support for live patching

On Fri, 21 Nov 2014, Josh Poimboeuf wrote:

> On Fri, Nov 21, 2014 at 03:44:35PM +0100, Miroslav Benes wrote:
> > On Fri, 21 Nov 2014, Jiri Kosina wrote:
> > 
> > [...]
> > 
> > > [ ... snip ... ]
> > > > +static int klp_init_patch(struct klp_patch *patch)
> > > > +{
> > > > +	int ret;
> > > > +
> > > > +	mutex_lock(&klp_mutex);
> > > > +
> > > > +	/* init */
> > > > +	patch->state = LPC_DISABLED;
> > > > +
> > > > +	/* sysfs */
> > > > +	ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
> > > > +				   klp_root_kobj, patch->mod->name);
> > > > +	if (ret)
> > > > +		return ret;
> > > 
> > > klp_mutex is leaked locked here.
> > > 
> > > > +
> > > > +	/* create objects */
> > > > +	ret = klp_init_objects(patch);
> > > > +	if (ret) {
> > > > +		kobject_put(&patch->kobj);
> > > > +		return ret;
> > > 
> > > And here as well.
> > > 
> > > All in all, this is looking very good to me. I think we are really close 
> > > to having a code that all the parties would agree with. Thanks everybody,
> > 
> > The leaking is my fault. I missed that somehow during rebasing.
> > 
> > Seth, could you please fix it in v4? 
> 
> Is it necessary to grab the mutex at the beginning of klp_init_patch?  I
> think we only need it when adding it to the global list at the end of
> the function.

I think it's not necessary now after thinking about that. It could happen 
that init values could be written twice to some patch structure if 
klp_register_patch would be called twice. But it should not corrupt 
anything and adding to the global list is protected. However I think we 
should define what is protected by klp_mutex and comment it somewhere near 
the mutex definition (if only the klp_patches list is protected or 
something more (in the future)).

Mira
--
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/