From: Andrey Konovalov <andreyknvl@gmail.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
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 21:44:00 +0200 [thread overview]
Message-ID: <CA+fCnZd9unSjY-UnEwc4rGkSRgZX3nrs=WgBb2eDQNEpZX10cA@mail.gmail.com> (raw)
In-Reply-To: <c0bd173c-c84f-41d5-8532-2afb8eca9313@csgroup.eu>
On Fri, Sep 5, 2025 at 9:13 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> > 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 ?
Ah, you're right, thanks!
I was confused by the name of kasan_populate_early_shadow(). I think
we should rename it to kasan_populate_shadow_read_only() or something
like that and also update the comment. As this function is not
intended for populating early shadow (that is done via
kasan_early_init() in the arch code instead), we're populating normal
shadow for pages that can be accessed but whose shadow won't be
written to. Perhaps it makes sense to come up with a better name for
the kasan_early_shadow_page variable too to point out its dual
purpose.
next prev parent reply other threads:[~2025-09-05 19:44 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-20 5:34 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
2025-09-05 19:44 ` Andrey Konovalov [this message]
2025-09-05 20:34 ` Andrey Konovalov
2025-09-06 13:25 ` Andrey Konovalov
2025-09-15 5:37 ` Baoquan He
2025-09-15 9:05 ` Baoquan He
2025-09-23 17:49 ` Andrey Konovalov
2025-09-24 2:35 ` Baoquan He
2025-09-24 21:07 ` Sabyrzhan Tasbolatov
2025-09-25 6:20 ` Baoquan He
2025-10-14 5:27 ` Sabyrzhan Tasbolatov
2025-10-14 9:14 ` Baoquan He
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