[PATCH] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC

[Andrew Morton]

On Fri, 26 Feb 2021 02:25:37 +0100 Andrey Konovalov <andreyknvl at google.com> wrote:

> Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
> after debug_pagealloc_unmap_pages(). This causes a crash when
> debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
> unmapped page.
> 
> This patch puts kasan_free_nondeferred_pages() before
> debug_pagealloc_unmap_pages().
> 
> Besides fixing the crash, this also makes the annotation order consistent
> with debug_pagealloc_map_pages() preceding kasan_alloc_pages().
> 

This bug exists in 5.12, does it not?

If so, is cc:stable appropriate and if so, do we have a suitable Fixes:
commit?

Thanks.