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Date:   Mon, 6 Aug 2018 08:06:49 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     =?utf-8?B?56a56Iif6ZSu?= <ufo19890607@gmail.com>
Cc:     Wind Yu <yuzhoujian@didichuxing.com>, rientjes@google.com,
        rong.a.chen@intel.com, sfr@canb.auug.org.au,
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        penguin-kernel@i-love.sakura.ne.jp, guro@fb.com,
        yang.s@alibaba-inc.com, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, lkp@01.org
Subject: Re: [LKP] [mm, oom] c1e4c54f9c: BUG:KASAN:null-ptr-deref_in_d
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On Sun 05-08-18 11:41:50, 禹舟键 wrote:
> Hi Michal and David,
> AFAICS, the null pointer is the task_struct of p in the dump_header.
> Why don't we just add a if before printing the victim task's
> informaiton.

See http://lkml.kernel.org/r/alpine.DEB.2.21.1807301854040.198273@chino.kir.corp.google.com

> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -438,14 +438,6 @@ static void dump_header(struct oom_control *oc,
> struct task_struct *p)
> 
>         cpuset_print_current_mems_allowed();
>         mem_cgroup_print_oom_context(oc->memcg, p);
> -       pr_cont(",task=%s,pid=%d,uid=%d\n", p->comm, p->pid,
> -               from_kuid(&init_user_ns, task_uid(p)));
> +      if (p)
> +              pr_cont(",task=%s,pid=%d,uid=%d", p->comm, p->pid,
> +                      from_kuid(&init_user_ns, task_uid(p)));
> +     pr_cont("\n");
>         if (is_memcg_oom(oc))
>                 mem_cgroup_print_oom_meminfo(oc->memcg);
> 
> Thanks
> Zhoujian

-- 
Michal Hocko
SUSE Labs