Re: [PATCH v2 00/34] kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS

[Andrey Konovalov <andreyknvl@gmail.com>]

On Mon, Dec 6, 2021 at 10:22 PM <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.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-v2
>
> 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.
>
> I'll keep the patchset based on the mainline for now. Once the
> high-level issues are resolved, I'll rebase onto mm - there might be
> a few conflicts right now.
>
> 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 v1->v2:
> - Move memory init for vmalloc() into vmalloc code for HW_TAGS KASAN.
> - Minor fixes and code reshuffling, see patches for lists of changes.
>
> Thanks!

FTR, I found a few issues with a tag propagating to PC (in BPF JIT and
a few other places). Will address them in v3.