linux-kernel - Re: [PATCH 2/2] kasan: add memcg kmem

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Date:   Thu, 22 Dec 2016 11:56:37 +0300
From:   Vladimir Davydov <vdavydov@...antool.org>
To:     Greg Thelen <gthelen@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kasan: add memcg kmem_cache test

On Tue, Dec 20, 2016 at 10:11:02AM -0800, Greg Thelen wrote:
> Make a kasan test which uses a SLAB_ACCOUNT slab cache.  If the test is
> run within a non default memcg, then it uncovers the bug fixed by
> "kasan: drain quarantine of memcg slab objects"[1].
> 
> If run without fix [1] it shows "Slab cache still has objects", and the
> kmem_cache structure is leaked.
> Here's an unpatched kernel test:
> $ dmesg -c > /dev/null
> $ mkdir /sys/fs/cgroup/memory/test
> $ echo $$ > /sys/fs/cgroup/memory/test/tasks
> $ modprobe test_kasan 2> /dev/null
> $ dmesg | grep -B1 still
> [ 123.456789] kasan test: memcg_accounted_kmem_cache allocate memcg accounted object
> [ 124.456789] kmem_cache_destroy test_cache: Slab cache still has objects
> 
> Kernels with fix [1] don't have the "Slab cache still has objects"
> warning or the underlying leak.
> 
> The new test runs and passes in the default (root) memcg, though in the
> root memcg it won't uncover the problem fixed by [1].
> 
> Signed-off-by: Greg Thelen <gthelen@...gle.com>

Reviewed-by: Vladimir Davydov <vdavydov.dev@...il.com>