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Date:   Fri, 11 Dec 2020 13:43:39 +0000
From:   Chris Down <chris@chrisdown.name>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>,
        "qiang.zhang@windriver.com" <qiang.zhang@windriver.com>,
        "sfr@canb.auug.org.au" <sfr@canb.auug.org.au>,
        "aryabinin@virtuozzo.com" <aryabinin@virtuozzo.com>,
        "dvyukov@google.com" <dvyukov@google.com>,
        "andreyknvl@google.com" <andreyknvl@google.com>,
        "qcai@redhat.com" <qcai@redhat.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        walter-zh.wu@mediatek.com
Subject: Re: [PATCH] kasan: fix slab double free when cpu-hotplug
Message-ID: <X9N3i+EwydXFc4HW@chrisdown.name>
References: <20201204102206.20237-1-qiang.zhang@windriver.com>
 <1607083295.22062.15.camel@mtksdccf07>
 <20201204172521.ed9f77164ff9f9fc91f35ee0@linux-foundation.org>
 <1607185035.22062.42.camel@mtksdccf07>
 <20201205170914.e380173074b2deded2ade3d3@linux-foundation.org>
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User-Agent: Mutt/2.0.3 (a51f058f) (2020-12-04)
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Hi folks,

Andrew Morton writes:
>@@ -188,6 +190,10 @@ void quarantine_put(struct kasan_free_me
> 	local_irq_save(flags);
>
> 	q = this_cpu_ptr(&cpu_quarantine);
>+	if (q->offline) {
>+		local_irq_restore(flags);
>+		return;
>+	}
> 	qlist_put(q, &info->quarantine_link, cache->size);
> 	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> 		qlist_move_all(q, &temp);

I'm afraid as well as the issues already identified, this also fails, because 
`quarantine_put` now returns a bool after "kasan: sanitize objects when 
metadata doesn't fit":

     mm/kasan/quarantine.c: In function ‘quarantine_put’:
     mm/kasan/quarantine.c:198:3: error: ‘return’ with no value, in function returning non-void [-Werror=return-type]
       198 |   return;
           |   ^~~~~~
     mm/kasan/quarantine.c:171:6: note: declared here
       171 | bool quarantine_put(struct kmem_cache *cache, void *object)