linux-kernel - Re: [PATCH v2 1/2] mm/damon: validate if the pmd entry is present before accessing

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: <20220820141702.e731f2aade5da8cbe0c78cba@linux-foundation.org>
Date:   Sat, 20 Aug 2022 14:17:02 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     sj@...nel.org, muchun.song@...ux.dev, mike.kravetz@...cle.com,
        damon@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm/damon: validate if the pmd entry is present
 before accessing

On Thu, 18 Aug 2022 15:37:43 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:

> The pmd_huge() is used to validate if the pmd entry is mapped by a huge
> page, also including the case of non-present (migration or hwpoisoned)
> pmd entry on arm64 or x86 architectures. That means the pmd_pfn() can
> not get the correct pfn number for the non-present pmd entry, which
> will cause damon_get_page() to get an incorrect page struct (also
> may be NULL by pfn_to_online_page()) to make the access statistics
> incorrect.
> 
> Moreover it does not make sense that we still waste time to get the
> page of the non-present entry, just treat it as not-accessed and skip it,
> that keeps consistent with non-present pte level entry.
> 
> Thus adding a pmd entry present validation to fix above issues.
> 

Do we have a Fixes: for this?

What are the user-visible runtime effects of the bug?  "make the access
statistics incorrect" is rather vague.

Do we feel that a cc:stable is warranted?