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SubjectRe: [PATCH 27/31] kasan, vmalloc: add vmalloc support to HW_TAGS
On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@linux.dev wrote:
> From: Andrey Konovalov <andreyknvl@google.com>
>
> This patch adds vmalloc tagging support to HW_TAGS KASAN.
>
> The key difference between HW_TAGS and the other two KASAN modes
> when it comes to vmalloc: HW_TAGS KASAN can only assign tags to
> physical memory. The other two modes have shadow memory covering
> every mapped virtual memory region.
>
> This patch makes __kasan_unpoison_vmalloc() for HW_TAGS KASAN:
>
> - Skip non-VM_ALLOC mappings as HW_TAGS KASAN can only tag a single
> mapping of normal physical memory; see the comment in the function.
> - Generate a random tag, tag the returned pointer and the allocation.
> - Propagate the tag into the page stucts to allow accesses through
> page_address(vmalloc_to_page()).
>
> The rest of vmalloc-related KASAN hooks are not needed:
>
> - The shadow-related ones are fully skipped.
> - __kasan_poison_vmalloc() is kept as a no-op with a comment.
>
> Poisoning of physical pages that are backing vmalloc() allocations
> is skipped via __GFP_SKIP_KASAN_UNPOISON: __kasan_unpoison_vmalloc()
> poisons them instead.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

This is missing a Signed-off-by from Vincenzo.

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