linux-kernel - Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting

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: <20211006175821.GA1941@duo.ucw.cz>
Date:   Wed, 6 Oct 2021 19:58:21 +0200
From:   Pavel Machek <pavel@....cz>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Colin Cross <ccross@...gle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Al Viro <viro@...iv.linux.org.uk>,
        Randy Dunlap <rdunlap@...radead.org>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        Peter Xu <peterx@...hat.com>, rppt@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        vincenzo.frascino@....com,
        Chinwen Chang (張錦文) 
        <chinwen.chang@...iatek.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jann Horn <jannh@...gle.com>, apopple@...dia.com,
        Yu Zhao <yuzhao@...gle.com>, Will Deacon <will@...nel.org>,
        fenghua.yu@...el.com, thunder.leizhen@...wei.com,
        Hugh Dickins <hughd@...gle.com>, feng.tang@...el.com,
        Jason Gunthorpe <jgg@...pe.ca>, Roman Gushchin <guro@...com>,
        Thomas Gleixner <tglx@...utronix.de>, krisman@...labora.com,
        chris.hyser@...cle.com, Peter Collingbourne <pcc@...gle.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Jens Axboe <axboe@...nel.dk>, legion@...nel.org,
        Rolf Eike Beer <eb@...ix.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Muchun Song <songmuchun@...edance.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Thomas Cedeno <thomascedeno@...gle.com>, sashal@...nel.org,
        cxfcosmos@...il.com, Rasmus Villemoes <linux@...musvillemoes.dk>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm <linux-mm@...ck.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting

Hi!

> > I can understand that having a string can be quite beneficial e.g., when
> > dumping mmaps. If only user space knows the id <-> string mapping, that
> > can be quite tricky.
> >
> > However, I also do wonder if there would be a way to standardize/reserve
> > ids, such that a given id always corresponds to a specific user. If we
> > use an uint64_t for an id, there would be plenty room to reserve ids ...
> >
> > I'd really prefer if we can avoid using strings and instead using ids.
> 
> I wish it was that simple and for some names like [anon:.bss] or
> [anon:dalvik-zygote space] reserving a unique id would work, however
> some names like [anon:dalvik-/system/framework/boot-core-icu4j.art]
> are generated dynamically at runtime and include package name.

I'd be careful; if you allow special characters like that, you will
confuse some kind of parser.

> Packages are constantly evolving, new ones are developed, names can
> change, etc. So assigning a unique id for these names is not really
> feasible.
> That leaves us with the central facility option, which as I described
> in my previous email would be prohibitive from performance POV (IPC
> every time we have a new name or want to convert id to name).

That "central facility" option can be as simple as "mkdir
/somewhere/sanitized_id", using inode numbers for example. You don't
really need IPC.

Plus, I don't really believe the IPC cost would be prohibitive.

Or you could simply hash the string and use the hash as id...

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

Download attachment "signature.asc" of type "application/pgp-signature" (196 bytes)