linux-kernel - Re: [PATCH] sched/core: Clear the root_domain cpumasks in init

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:	Fri, 4 Dec 2015 09:30:54 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Xunlei Pang <xlpang@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] sched/core: Clear the root_domain cpumasks in
 init_rootdomain()


* Xunlei Pang <xlpang@...hat.com> wrote:

> Hi Ingo,
> 
> On 12/04/2015 at 04:09 PM, Ingo Molnar wrote:
> > * Xunlei Pang <xlpang@...hat.com> wrote:
> >
> >>> Hm, is the alloc_cpumask_var() done in alloc_sched_domains() safe?
> >> Until now, I haven't found any other similar issues, but I will check further.
> >>
> >>> At least the usage pattern in init_sched_domains() looks unsafe:
> >>>
> >>>         doms_cur = alloc_sched_domains(ndoms_cur);
> >>>         if (!doms_cur)
> >>>                 doms_cur = &fallback_doms;
> >>>         cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
> > So is this pattern in init_sched_domains() correct, for OFFSTACK=y?
> >
> > It looks wrong to me, as alloc_sched_domains() allocates an uninitialized cpumask 
> > via alloc_cpumask_var() and returns it:
> >
> > cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
> > {
> >         int i;
> >         cpumask_var_t *doms;
> >
> >         doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
> >         if (!doms)
> >                 return NULL;
> >         for (i = 0; i < ndoms; i++) {
> >                 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
> >                         free_sched_domains(doms, i);
> >                         return NULL;
> >                 }
> >         }
> >         return doms;
> > }
> >
> > and then this code:
> >
> >>>         cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
> > uses it without first clearing it.
> >
> > So is this another such bug, or am I missing something?
> 
> Yeah, I noticed that as well. But fortunately cpumask_andnot(), 
> cpumask_and() and the like will clear doms_cur[] indirectly, also
> cpu_isolated_map, cpu_active_mask, etc doesn't contain any
> garbage bits. I also checked the use of it by cpuset, no extra such
> bug found by me so far.

Great, thanks for double checking!

	Ingo
--
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/