linux-kernel - Re: [PATCH v2] kmemleak: survive in a low-memory situation

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]

Message-ID: <20190103093201.GB31793@dhcp22.suse.cz>
Date:   Thu, 3 Jan 2019 10:32:01 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     catalin.marinas@....com, akpm@...ux-foundation.org, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kmemleak: survive in a low-memory situation

On Wed 02-01-19 13:06:19, Qian Cai wrote:
[...]
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index f9d9dc250428..9e1aa3b7df75 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -576,6 +576,16 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
>  	struct rb_node **link, *rb_parent;
>  
>  	object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
> +#ifdef CONFIG_PREEMPT_COUNT
> +	if (!object) {
> +		/* last-ditch effort in a low-memory situation */
> +		if (irqs_disabled() || is_idle_task(current) || in_atomic())
> +			gfp = GFP_ATOMIC;
> +		else
> +			gfp = gfp_kmemleak_mask(gfp) | __GFP_DIRECT_RECLAIM;
> +		object = kmem_cache_alloc(object_cache, gfp);
> +	}
> +#endif

I do not get it. How can this possibly help when gfp_kmemleak_mask()
adds __GFP_NOFAIL modifier to the given gfp mask? Or is this not the
case anymore in some tree?
-- 
Michal Hocko
SUSE Labs