linux-kernel - Re: WARNING in memory_failure() at include/linux/huge

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 for Android: free password hash cracker in your pocket

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

Message-ID: <e97d5c0c-b8ec-4da4-b838-7a308f8a6327@kernel.org>
Date: Wed, 4 Feb 2026 20:18:14 +0100
From: "David Hildenbrand (arm)" <david@...nel.org>
To: Zi Yan <ziy@...dia.com>
Cc: 是参差 <shicenci@...il.com>, linux-mm@...ck.org,
 linmiaohe@...wei.com, akpm@...ux-foundation.org,
 linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: WARNING in memory_failure() at include/linux/huge_mm.h:635
 triggered

On 2/4/26 18:41, Zi Yan wrote:
> On 4 Feb 2026, at 12:34, Zi Yan wrote:
> 
>> On 4 Feb 2026, at 12:23, Zi Yan wrote:
>>
>>>
>>>
>>>  From the C repro above, syzbot opened a dev "/dev/sg#" and did mmap on it.
>>> Is it a device driver issue?
>>
>> OK, it is CONFIG_CHR_DEV_SG. And the driver allocates a compound page at[1].
>> Since we initialize folio fields in prep_compound_page(), it becomes a folio
>> when it is inserted into a VMA.
> 
> More details:
> later at sg_vma_fault(), the driver just handles a page fault by supplying
> a subpage from a pre-allocated compound page[3]. We then get a large folio
> without !CONFIG_TRANSPARENT_HUGEPAGE.

We can identify such non-folio (but compound) things by looking at 
PG_large_rmappable IIRC.

-- 
Cheers,

David