linux-kernel - Re: [PATCH] kasan: fix slab double free when cpu-hotplug

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Message-ID: <X9N3i+EwydXFc4HW@chrisdown.name>
Date:   Fri, 11 Dec 2020 13:43:39 +0000
From:   Chris Down <chris@...isdown.name>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>,
        "qiang.zhang@...driver.com" <qiang.zhang@...driver.com>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "aryabinin@...tuozzo.com" <aryabinin@...tuozzo.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "andreyknvl@...gle.com" <andreyknvl@...gle.com>,
        "qcai@...hat.com" <qcai@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        walter-zh.wu@...iatek.com
Subject: Re: [PATCH] kasan: fix slab double free when cpu-hotplug

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)