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Date:   Wed, 3 Mar 2021 15:23:55 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Christoph Hellwig <hch@infradead.org>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC
Message-Id: <20210303152355.fa7c3bcb02862ceefea5ca45@linux-foundation.org>
In-Reply-To: <1aa83e48627978de8068d5e3314185f3a0d7a849.1614302398.git.andreyknvl@google.com>
References: <1aa83e48627978de8068d5e3314185f3a0d7a849.1614302398.git.andreyknvl@google.com>
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On Fri, 26 Feb 2021 02:25:37 +0100 Andrey Konovalov <andreyknvl@google.com> wrote:

> Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
> after debug_pagealloc_unmap_pages(). This causes a crash when
> debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
> unmapped page.
> 
> This patch puts kasan_free_nondeferred_pages() before
> debug_pagealloc_unmap_pages().
> 
> Besides fixing the crash, this also makes the annotation order consistent
> with debug_pagealloc_map_pages() preceding kasan_alloc_pages().
> 

This bug exists in 5.12, does it not?

If so, is cc:stable appropriate and if so, do we have a suitable Fixes:
commit?

Thanks.