On Thu, Mar 4, 2021 at 12:23 AM Andrew Morton akpm@linux-foundation.org wrote:

On Fri, 26 Feb 2021 02:25:37 +0100 Andrey Konovalov andreyknvl@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?

Sure:

Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS") Cc: stable@vger.kernel.org