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Date: Wed, 23 Dec 2015 14:38:13 -0700
From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Tejun Heo <tj@kernel.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Li Zefan <lizefan@huawei.com>,
        Daniel Wagner <daniel.wagner@bmw-carit.de>,
        Johannes Weiner <hannes@cmpxchg.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, Dave Jones <davej@codemonkey.org.uk>,
        kernel-team@fb.com, Aleksa Sarai <cyphar@cyphar.com>,
        Michal Hocko <mhocko@kernel.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Neil Horman <nhorman@tuxdriver.com>
Subject: Re: [PATCH] cgroup: Fix uninitialized variable warning
Message-ID: <20151223213813.GA21287@linux.intel.com>
References: <1450906240-21821-1-git-send-email-ross.zwisler@linux.intel.com>
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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...