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Date:   Fri, 11 Dec 2020 11:39:09 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Chris Down <chris@chrisdown.name>
Cc:     Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>,
        "qiang.zhang@windriver.com" <qiang.zhang@windriver.com>,
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        "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: <20201211113909.230e68fcb66193aa71661ddd@linux-foundation.org>
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On Fri, 11 Dec 2020 13:43:39 +0000 Chris Down <chris@chrisdown.name> wrote:

> 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)

Yup, thanks.  I think I have this all fixed now, using the old
apply-one-patch-compile-everything-repeat approach.