From: Christoph Lameter <cl@linux.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Kees Cook <keescook@chromium.org>,
gthelen@google.com, labbott@fedoraproject.org,
kernel-hardening@lists.openwall.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v4] mm: SLAB freelist randomization
Date: Wed, 27 Apr 2016 10:39:29 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1604271027540.20042@east.gentwo.org> (raw)
In-Reply-To: <20160426161743.f831225a4efb3eb04debe402@linux-foundation.org>
On Tue, 26 Apr 2016, Andrew Morton wrote:
> : CONFIG_FREELIST_RANDOM bugs me a bit - "freelist" is so vague.
> : CONFIG_SLAB_FREELIST_RANDOM would be better. I mean, what Kconfig
> : identifier could be used for implementing randomisation in
> : slub/slob/etc once CONFIG_FREELIST_RANDOM is used up?
>
> but this pearl appeared to pass unnoticed.
Ok. lets add SLAB here and then use this option for the other allocators
as well.
> > + /* If it fails, we will just use the global lists */
> > + cachep->random_seq = kcalloc(count, sizeof(freelist_idx_t), GFP_KERNEL);
> > + if (!cachep->random_seq)
> > + return -ENOMEM;
>
> OK, no BUG. If this happens, kmem_cache_init_late() will go BUG
> instead ;)
>
> Questions for slab maintainers:
>
> What's going on with the gfp_flags in there? kmem_cache_init_late()
> passes GFP_NOWAIT into enable_cpucache().
>
> a) why the heck does it do that? It's __init code!
enable_cpucache() was called when a slab cache was reconfigured by writing to /proc/slabinfo.
That was changed awhile back when the memcg changes were made ot slab. So
now its ok to be made init code.
> Finally, all callers of enable_cpucache() (and hence of
> cache_random_seq_create()) are __init, so we're unnecessarily bloating
> up vmlinux. Could someone please take a look at this as a separate
> thing?
Hmmm. Well if that is the case then lots of stuff could be straightened
out. Joonsoo?
next prev parent reply other threads:[~2016-04-27 15:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 16:21 [PATCH v4] mm: SLAB freelist randomization Thomas Garnier
2016-04-26 23:17 ` Andrew Morton
2016-04-26 23:22 ` Thomas Garnier
2016-04-27 15:40 ` Christoph Lameter
2016-04-27 0:55 ` Joonsoo Kim
2016-04-27 15:39 ` Christoph Lameter [this message]
2016-04-29 7:18 ` Joonsoo Kim
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