linux-kernel - Re: [PATCH] cgroup: Fix uninitialized variable warning

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Message-ID: <20151223213813.GA21287@linux.intel.com>
Date:	Wed, 23 Dec 2015 14:38:13 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Li Zefan <lizefan@...wei.com>,
	Daniel Wagner <daniel.wagner@...-carit.de>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Dave Jones <davej@...emonkey.org.uk>,
	kernel-team@...com, Aleksa Sarai <cyphar@...har.com>,
	Michal Hocko <mhocko@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH] cgroup: Fix uninitialized variable warning

On Wed, Dec 23, 2015 at 04:35:19PM -0500, Tejun Heo wrote:
> Hello, Ross.
> 
> On Wed, Dec 23, 2015 at 02:30:40PM -0700, Ross Zwisler wrote:
> >  static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
> >  {
> >  	struct cgroup_subsys_state *css;
> > -	struct mem_cgroup *memcg;
> > +	struct mem_cgroup *memcg = NULL;
> 
> It's one thing to add spurious init to shut up gcc
> 
> > @@ -4805,7 +4805,7 @@ static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
> >  		p = leader;
> >  		memcg = mem_cgroup_from_css(css);
> >  	}
> > -	if (!p)
> > +	if (!p || !memcg)
> 
> and to another to add an additional processing on it.

Do you believe that the additional processing is incorrect?  If somehow we
*do* get through the above loop without setting memcg, the next deref will
OOPs the kernel...
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