linux-kernel - Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region

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: <xbgdq47laus4mmm5sobkevjdrs2km5virq3gqperutdifuf47l@b7o5qmn7ckfd>
Date: Tue, 23 Jul 2024 13:58:43 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>, Al Viro <viro@...iv.linux.org.uk>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "Kirill A . Shutemov" <kirill@...temov.name>, x86@...nel.org,
        Yan Zhao <yan.y.zhao@...el.com>, Kevin Tian <kevin.tian@...el.com>,
        Pei Li <peili.dev@...il.com>, David Wang <00107082@....com>,
        Bert Karwatzki <spasswolf@....de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region

* David Hildenbrand <david@...hat.com> [240723 06:12]:
> On 22.07.24 23:17, Peter Xu wrote:
> > On Mon, Jul 22, 2024 at 04:22:45PM -0400, Liam R. Howlett wrote:
> > > The problem report from [2] and [3] is that we are getting to a call
> > > path that includes unmap_single_vma() without the mmap lock.  This patch
> > > fails to address that issue, it only takes the caller with the assert
> > > out of the call path.
> > > 
> > > Removing the function with the lock check doesn't fix the locking issue.
> > > If there is no locking issue here, please state the case in the commit
> > > log as you feel it is safe to use a vma pointer without the mmap_lock
> > > held.
> > 
> > Could you please state why there's a locking issue, and why this patch (of
> > a x86 PAT specific issue...) would need any documentation on that?
> > 
> > I thought it was pretty common that file truncation (or anything similar)
> > does a file rmap walk over vmas that mapping this file, and vmas need to be
> > alive during the rmap walk, no?
> 
> Right, I was also assuming that the rmap locking (from where we obtained
> that VMA -- rmap interval tree) makes sure that using the VMA is safe.
> 

Ah, that's what I was missing.

Might be worth adding to the change log.

Thanks,
Liam