linux-kernel - Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fccbce9c-a40e-621f-e9a4-17c327ed84e8@I-love.SAKURA.ne.jp>
Date:   Thu, 28 Sep 2017 13:36:57 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Yang Shi <yang.s@...baba-inc.com>, mhocko@...nel.org
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom
 message

On 2017/09/28 6:46, Yang Shi wrote:
> Changelog v7 —> v8:
> * Adopted Michal’s suggestion to dump unreclaim slab info when unreclaimable slabs amount > total user memory. Not only in oom panic path.

Holding slab_mutex inside dump_unreclaimable_slab() was refrained since V2
because there are

	mutex_lock(&slab_mutex);
	kmalloc(GFP_KERNEL);
	mutex_unlock(&slab_mutex);

users. If we call dump_unreclaimable_slab() for non OOM panic path, aren't we
introducing a risk of crash (i.e. kernel panic) for regular OOM path?

We can try mutex_trylock() from dump_unreclaimable_slab() at best.
But it is still remaining unsafe, isn't it?