From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Andrey Konovalov <andreyknvl@gmail.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Baoquan He <bhe@redhat.com>,
snovitoll@gmail.com, glider@google.com, dvyukov@google.com,
elver@google.com, linux-mm@kvack.org, vincenzo.frascino@arm.com,
akpm@linux-foundation.org, kasan-dev@googlegroups.com,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
sj@kernel.org, lorenzo.stoakes@oracle.com
Subject: Re: [PATCH v3 00/12] mm/kasan: make kasan=on|off work for all three modes
Date: Fri, 5 Sep 2025 21:13:28 +0200 [thread overview]
Message-ID: <c0bd173c-c84f-41d5-8532-2afb8eca9313@csgroup.eu> (raw)
In-Reply-To: <CA+fCnZdWxWD99t9yhmB90VPefi3Gohn8Peo6=cxrvw8Zdz+3qQ@mail.gmail.com>
Le 05/09/2025 à 20:08, Andrey Konovalov a écrit :
> On Fri, Sep 5, 2025 at 7:12 PM Andrey Ryabinin <ryabinin.a.a@gmail.com> wrote:
>>
>>> But have you tried running kasan=off + CONFIG_KASAN_STACK=y +
>>> CONFIG_VMAP_STACK=y (+ CONFIG_KASAN_VMALLOC=y)? I would expect this
>>> should causes crashes, as the early shadow is mapped as read-only and
>>> the inline stack instrumentation will try writing into it (or do the
>>> writes into the early shadow somehow get ignored?..).
>>>
>>
>> It's not read-only, otherwise we would crash very early before full shadow
>> setup and won't be able to boot at all. So writes still happen, and shadow
>> checked, but reports are disabled.
>
> Hm, I thought it worked like that, but then what threw me off just now
> was seeing that zero_pte_populate()->pte_wrprotect() (on arm64) resets
> the PTE_WRITE bit and sets the PTE_RDONLY bit. So I thought the
> kasan_early_shadow_page is marked as read-only and then the
> instrumentation is disabled for all early code that might write into
> the page before the proper shadow is set up. Or am I reading this
> bit-setting code wrong?
But that zero_pte_populate() is called by kasan_init() when everything
is ready.
kasan_init()->kasan_init_shadow()->kasan_populate_early_shadow()->zero_p4d_populate()->zero_pud_populate()->zero_pmd_populate()->zero_pte_populate()
Here we are talking about the shadow set at startup kasan_early_init(),
aren't we ?
Christophe
next prev parent reply other threads:[~2025-09-05 19:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-20 5:34 [PATCH v3 00/12] mm/kasan: make kasan=on|off work for all three modes Baoquan He
2025-08-20 5:34 ` [PATCH v3 01/12] mm/kasan: add conditional checks in functions to return directly if kasan is disabled Baoquan He
2025-08-20 5:34 ` [PATCH v3 02/12] mm/kasan: move kasan= code to common place Baoquan He
2025-08-20 5:34 ` [PATCH v3 03/12] mm/kasan/sw_tags: don't initialize kasan if it's disabled Baoquan He
2025-08-20 5:34 ` [PATCH v3 04/12] arch/arm: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 05/12] arch/arm64: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 06/12] arch/loongarch: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 07/12] arch/powerpc: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 08/12] arch/riscv: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 09/12] arch/x86: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 10/12] arch/xtensa: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 11/12] arch/um: " Baoquan He
2025-08-20 5:34 ` [PATCH v3 12/12] mm/kasan: make kasan=on|off take effect for all three modes Baoquan He
2025-09-03 13:22 ` [PATCH v3 00/12] mm/kasan: make kasan=on|off work " Andrey Konovalov
2025-09-04 8:11 ` Baoquan He
2025-09-04 14:58 ` Andrey Konovalov
2025-09-05 17:12 ` Andrey Ryabinin
2025-09-05 18:08 ` Andrey Konovalov
2025-09-05 19:13 ` Christophe Leroy [this message]
2025-09-05 19:44 ` Andrey Konovalov
2025-09-05 20:34 ` Andrey Konovalov
2025-09-06 13:25 ` Andrey Konovalov
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