linux-kernel - Re: [PATCH v2] mm: make page_mapped_in

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

Message-ID: <0e825585-3421-4fa9-8912-41b936f29fae@redhat.com>
Date: Wed, 26 Feb 2025 16:49:32 +0100
From: David Hildenbrand <david@...hat.com>
To: Jane Chu <jane.chu@...cle.com>, willy@...radead.org, peterx@...hat.com,
 akpm@...ux-foundation.org, linmiaohe@...wei.com,
 kirill.shutemov@...ux.intel.com, hughd@...gle.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: make page_mapped_in_vma() hugetlb walk aware

On 24.02.25 22:14, Jane Chu wrote:
> When a process consumes a UE in a page, the memory failure handler
> attempts to collect information for a potential SIGBUS.
> If the page is an anonymous page, page_mapped_in_vma(page, vma) is
> invoked in order to
>    1. retrieve the vaddr from the process' address space,
>    2. verify that the vaddr is indeed mapped to the poisoned page,
> where 'page' is the precise small page with UE.
> 
> It's been observed that when injecting poison to a non-head subpage
> of an anonymous hugetlb page, no SIGBUS show up; while injecting to
> the head page produces a SIGBUS. The casue is that, though hugetlb_walk()
> returns a valid pmd entry (on x86), but check_pte() detects mismatch
> between the head page per the pmd and the input subpage. Thus the vaddr
> is considered not mapped to the subpage and the process is not collected
> for SIGBUS purpose.  This is the calling stack
>        collect_procs_anon
>          page_mapped_in_vma
>            page_vma_mapped_walk
>              hugetlb_walk
>                huge_pte_lock
>                  check_pte
> 

Why can't we require callers to never pass in subpages of hugetlb pages, 
and sanity check that this is the case?


-- 
Cheers,

David / dhildenb