On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@linux.dev wrote:

From: Andrey Konovalov <redacted>

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 <redacted>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

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

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