Date:   Tue, 14 Dec 2021 13:25:19 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     andrey.konovalov@linux.dev
Cc:     Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH mm v3 23/38] kasan, arm64: reset pointer tags of vmapped
 stacks
Message-ID: <YbibPyHQXjU2A/jg@arm.com>
References: <cover.1639432170.git.andreyknvl@google.com>
 <bc9f6cb3df24eb076a6d99f91f97820718f3e29e.1639432170.git.andreyknvl@google.com>
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On Mon, Dec 13, 2021 at 10:54:19PM +0100, andrey.konovalov@linux.dev wrote:
> From: Andrey Konovalov <andreyknvl@google.com>
> 
> Once tag-based KASAN modes start tagging vmalloc() allocations,
> kernel stacks start getting tagged if CONFIG_VMAP_STACK is enabled.
> 
> Reset the tag of kernel stack pointers after allocation in
> arch_alloc_vmap_stack().
> 
> For SW_TAGS KASAN, when CONFIG_KASAN_STACK is enabled, the
> instrumentation can't handle the SP register being tagged.
> 
> For HW_TAGS KASAN, there's no instrumentation-related issues. However,
> the impact of having a tagged SP register needs to be properly evaluated,
> so keep it non-tagged for now.
> 
> Note, that the memory for the stack allocation still gets tagged to
> catch vmalloc-into-stack out-of-bounds accesses.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>