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

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Message-ID: <54CB622C-0BB0-4772-A939-162D63433A00@nvidia.com>
Date: Tue, 13 Jan 2026 16:05:59 -0500
From: Zi Yan <ziy@...dia.com>
To: Boudewijn van der Heide <boudewijn@...ta-utec.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Vlastimil Babka <vbabka@...e.cz>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Brendan Jackman <jackmanb@...gle.com>,
 Johannes Weiner <hannes@...xchg.org>,
 Naoya Horiguchi <nao.horiguchi@...il.com>,
 Oscar Salvador <osalvador@...e.de>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Miaohe Lin <linmiaohe@...wei.com>
Subject: Re: [PATCH] mm/page_alloc: Fix freeing of failed-split poisoned
 compound pages

Add Miaohe (memory failure maintainer)

On 13 Jan 2026, at 15:54, Boudewijn van der Heide wrote:

> 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.

This is not a fix. IIUC, for >0 order free pages, memory failure uses
take_page_off_buddy() in a different code path.

Miaohe (cc’d) should be able to elaborate more on it.

>
> Fixes: 79f5f8fab482 ("mm,hwpoison: rework soft offline for in-use pages")
> Signed-off-by: Boudewijn van der Heide <boudewijn@...ta-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


Best Regards,
Yan, Zi