Re: [PATCH 27/31] kasan, vmalloc: add vmalloc support to HW_TAGS

[Andrey Konovalov]

On Fri, Dec 3, 2021 at 1:41 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@xxxxxxxxx wrote:
> > From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Co-developed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
>
> This is missing a Signed-off-by from Vincenzo.

I didn't add it myself as the patch is significantly modified from its
original version.

I'll ask Vincenzo to review when I send v2.

Thanks!