linux-kernel - Re: [RFC mm v6] mm: introduce a new page type for page pool in page type

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <e470c73a-9867-4387-9a9a-a63cd3b2654f@kernel.org>
Date: Mon, 17 Nov 2025 17:47:05 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Jesper Dangaard Brouer <hawk@...nel.org>,
 Byungchul Park <byungchul@...com>, linux-mm@...ck.org, netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
 harry.yoo@...cle.com, ast@...nel.org, daniel@...earbox.net,
 davem@...emloft.net, kuba@...nel.org, john.fastabend@...il.com,
 sdf@...ichev.me, saeedm@...dia.com, leon@...nel.org, tariqt@...dia.com,
 mbloch@...dia.com, andrew+netdev@...n.ch, edumazet@...gle.com,
 pabeni@...hat.com, akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
 mhocko@...e.com, horms@...nel.org, jackmanb@...gle.com, hannes@...xchg.org,
 ziy@...dia.com, ilias.apalodimas@...aro.org, willy@...radead.org,
 brauner@...nel.org, kas@...nel.org, yuzhao@...gle.com,
 usamaarif642@...il.com, baolin.wang@...ux.alibaba.com,
 almasrymina@...gle.com, toke@...hat.com, asml.silence@...il.com,
 bpf@...r.kernel.org, linux-rdma@...r.kernel.org, sfr@...b.auug.org.au,
 dw@...idwei.uk, ap420073@...il.com, dtatulea@...dia.com
Subject: Re: [RFC mm v6] mm: introduce a new page type for page pool in page
 type

On 17.11.25 17:02, Jesper Dangaard Brouer wrote:
> 
> On 17/11/2025 06.20, Byungchul Park wrote:
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 600d9e981c23..01dd14123065 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1041,7 +1041,6 @@ static inline bool page_expected_state(struct page *page,
>>    #ifdef CONFIG_MEMCG
>>    			page->memcg_data |
>>    #endif
>> -			page_pool_page_is_pp(page) |
>>    			(page->flags.f & check_flags)))
>>    		return false;
>>    
>> @@ -1068,8 +1067,6 @@ static const char *page_bad_reason(struct page *page, unsigned long flags)
>>    	if (unlikely(page->memcg_data))
>>    		bad_reason = "page still charged to cgroup";
>>    #endif
>> -	if (unlikely(page_pool_page_is_pp(page)))
>> -		bad_reason = "page_pool leak";
>>    	return bad_reason;
>>    }
> 
> This code have helped us catch leaks in the past.
> When this happens the result is that the page is marked as a bad page.
> 
>>    
>> @@ -1378,9 +1375,12 @@ __always_inline bool free_pages_prepare(struct page *page,
>>    		mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
>>    		folio->mapping = NULL;
>>    	}
>> -	if (unlikely(page_has_type(page)))
>> +	if (unlikely(page_has_type(page))) {
>> +		/* networking expects to clear its page type before releasing */
>> +		WARN_ON_ONCE(PageNetpp(page));
>>    		/* Reset the page_type (which overlays _mapcount) */
>>    		page->page_type = UINT_MAX;
>> +	}
>>    
>>    	if (is_check_pages_enabled()) {
>>    		if (free_page_is_bad(page))
> 
> What happens to the page? ... when it gets marked with:
>     page->page_type = UINT_MAX
> 
> Will it get freed and allowed to be used by others?
> - if so it can result in other hard-to-catch bugs

Yes, just like most other use-after-free from any other subsystem in the 
kernel :)

The expectation is that such BUGs are found early during testing 
(triggering a WARN) such that they can be fixed early.

But we could also report a bad page here and just stop (return false).

-- 
Cheers

David