linux-kernel - Re: [PATCH mm v4 00/39] kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW

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Date:   Wed, 22 Dec 2021 08:00:00 +0100
From:   Marco Elver <elver@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH mm v4 00/39] kasan, vmalloc, arm64: add vmalloc tagging
 support for SW/HW_TAGS

On Mon, 20 Dec 2021 at 22:58, <andrey.konovalov@...ux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@...gle.com>
>
> Hi,
>
> This patchset adds vmalloc tagging support for SW_TAGS and HW_TAGS
> KASAN modes.
>
> The tree with patches is available here:
>
> https://github.com/xairy/linux/tree/up-kasan-vmalloc-tags-v4-akpm
>
> About half of patches are cleanups I went for along the way. None of
> them seem to be important enough to go through stable, so I decided
> not to split them out into separate patches/series.
>
> The patchset is partially based on an early version of the HW_TAGS
> patchset by Vincenzo that had vmalloc support. Thus, I added a
> Co-developed-by tag into a few patches.
>
> SW_TAGS vmalloc tagging support is straightforward. It reuses all of
> the generic KASAN machinery, but uses shadow memory to store tags
> instead of magic values. Naturally, vmalloc tagging requires adding
> a few kasan_reset_tag() annotations to the vmalloc code.
>
> HW_TAGS vmalloc tagging support stands out. HW_TAGS KASAN is based on
> Arm MTE, which can only assigns tags to physical memory. As a result,
> HW_TAGS KASAN only tags vmalloc() allocations, which are backed by
> page_alloc memory. It ignores vmap() and others.
>
> Changes in v3->v4:
[...]
> Andrey Konovalov (39):
>   kasan, page_alloc: deduplicate should_skip_kasan_poison
>   kasan, page_alloc: move tag_clear_highpage out of
>     kernel_init_free_pages
>   kasan, page_alloc: merge kasan_free_pages into free_pages_prepare
>   kasan, page_alloc: simplify kasan_poison_pages call site
>   kasan, page_alloc: init memory of skipped pages on free
>   kasan: drop skip_kasan_poison variable in free_pages_prepare
>   mm: clarify __GFP_ZEROTAGS comment
>   kasan: only apply __GFP_ZEROTAGS when memory is zeroed
>   kasan, page_alloc: refactor init checks in post_alloc_hook
>   kasan, page_alloc: merge kasan_alloc_pages into post_alloc_hook
>   kasan, page_alloc: combine tag_clear_highpage calls in post_alloc_hook
>   kasan, page_alloc: move SetPageSkipKASanPoison in post_alloc_hook
>   kasan, page_alloc: move kernel_init_free_pages in post_alloc_hook
>   kasan, page_alloc: rework kasan_unpoison_pages call site
>   kasan: clean up metadata byte definitions
>   kasan: define KASAN_VMALLOC_INVALID for SW_TAGS
>   kasan, x86, arm64, s390: rename functions for modules shadow
>   kasan, vmalloc: drop outdated VM_KASAN comment
>   kasan: reorder vmalloc hooks
>   kasan: add wrappers for vmalloc hooks
>   kasan, vmalloc: reset tags in vmalloc functions
>   kasan, fork: reset pointer tags of vmapped stacks
>   kasan, arm64: reset pointer tags of vmapped stacks
>   kasan, vmalloc: add vmalloc tagging for SW_TAGS
>   kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged
>   kasan, vmalloc: unpoison VM_ALLOC pages after mapping
>   kasan, mm: only define ___GFP_SKIP_KASAN_POISON with HW_TAGS
>   kasan, page_alloc: allow skipping unpoisoning for HW_TAGS
>   kasan, page_alloc: allow skipping memory init for HW_TAGS
>   kasan, vmalloc: add vmalloc tagging for HW_TAGS
>   kasan, vmalloc: only tag normal vmalloc allocations
>   kasan, arm64: don't tag executable vmalloc allocations
>   kasan: mark kasan_arg_stacktrace as __initdata
>   kasan: simplify kasan_init_hw_tags
>   kasan: add kasan.vmalloc command line flag
>   kasan: allow enabling KASAN_VMALLOC and SW/HW_TAGS
>   arm64: select KASAN_VMALLOC for SW/HW_TAGS modes
>   kasan: documentation updates
>   kasan: improve vmalloc tests

Functionally it all looks good. So rather than acking every patch, for
the whole series:

Acked-by: Marco Elver <elver@...gle.com>

... and in case you do a v5, I've left some minor comments.

Happy holidays!

Thanks,
-- Marco