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Date:   Mon, 1 Aug 2022 10:13:04 +0200 (CEST)
From:   Christoph Lameter <cl@gentwo.de>
To:     Feng Tang <feng.tang@intel.com>
cc:     Dmitry Vyukov <dvyukov@google.com>,
        "Sang, Oliver" <oliver.sang@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>, lkp <lkp@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "lkp@lists.01.org" <lkp@lists.01.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        John Garry <john.garry@huawei.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        "kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>
Subject: Re: [mm/slub] 3616799128:
 BUG_kmalloc-#(Not_tainted):kmalloc_Redzone_overwritten
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References: <20220727071042.8796-4-feng.tang@intel.com> <YuYm3dWwpZwH58Hu@xsang-OptiPlex-9020> <YuY6Wc39DbL3YmGi@feng-skl> <Yudw5ge/lJ26Hksk@feng-skl> <CACT4Y+Y5aTQMuUU3j60KbLrH_DoFWq1e7EEF5Ka0c1F9a3FniA@mail.gmail.com> <YueFZm1JHDZOKVw/@feng-skl>
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On Mon, 1 Aug 2022, Feng Tang wrote:

> > Or does it make sense to prohibit KASAN+SLUB_DEBUG combination? Does
> > SLUB_DEBUG add anything on top of KASAN?
>
> I did a quick glance, seems the KASAN will select SLUB_DEBUG in
> many cases, as shown in the lib/Kconfig.kasan:
>
> 	config KASAN_GENERIC
> 		...
> 		select SLUB_DEBUG if SLUB
>
> 	config KASAN_SW_TAGS
> 		...
> 		select SLUB_DEBUG if SLUB

SLUB_DEBUG is on by default on all distros. This just means that debugging
support is compiled in but not activated. Kasan etc could depend on
SLUB_DEBUG. Without SLUB_DEBUG the debugging infrastructure of SLUB that
is use by Kasan is not included.

If you want to enable debugging on bootup then you need to set
SLUB_DEBUG_ON.