[PATCH] mm/page_alloc: Fix freeing of failed-split poisoned compound pages

[Boudewijn van der Heide <boudewijn@delta-utec.com>]

free_pages_prepare() only handles poisoned order-0 pages.
In memory_failure() (hard offline), pages
are poisoned before attempting to split huge pages. If the split fails,
the page remains a compound (order > 0) but is already poisoned. However,
Soft-offline pages are always poisoned as order-0 after migration, so
they are unaffected.

The '!order' check causes these poisoned compound pages to skip
poison handling, leaving them in the buddy allocator.

Worst case, a poisoned compound page could be reallocated,
potentially leading to crashes, silent data corruption,
or unwanted memory containment actions before the poison bit is detected.

This patch removes the '&& !order' restriction. Cleanup functions in the
poison-handling block correctly handle non-zero order pages, making
this change safe.

Fixes: 79f5f8fab482 ("mm,hwpoison: rework soft offline for in-use pages")
Signed-off-by: Boudewijn van der Heide <boudewijn@delta-utec.com>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c380f063e8b7..64d15e56706c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1344,7 +1344,7 @@ __always_inline bool free_pages_prepare(struct page *page,
 		count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
 	}
 
-	if (unlikely(PageHWPoison(page)) && !order) {
+	if (unlikely(PageHWPoison(page))) {
 		/* Do not let hwpoison pages hit pcplists/buddy */
 		reset_page_owner(page, order);
 		page_table_check_free(page, order);
-- 
2.47.3