netdev - Re: [PATCH net-next v4 1/4] mm: add a signature in struct page

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: <CAC_iWj+Tw9DzzzVj-F9AwzBN_OJV_HN2miJT4KTBH_Uei_V2ZA@mail.gmail.com>
Date:   Tue, 11 May 2021 17:25:36 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Matteo Croce <mcroce@...ux.microsoft.com>,
        Networking <netdev@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Ayush Sawal <ayush.sawal@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        Mirko Lindner <mlindner@...vell.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Boris Pismenny <borisp@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Yu Zhao <yuzhao@...gle.com>,
        Will Deacon <will@...nel.org>,
        Michel Lespinasse <walken@...gle.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Roman Gushchin <guro@...com>, Hugh Dickins <hughd@...gle.com>,
        Peter Xu <peterx@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexander Lobakin <alobakin@...me>,
        Cong Wang <cong.wang@...edance.com>, wenxu <wenxu@...oud.cn>,
        Kevin Hao <haokexin@...il.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Marco Elver <elver@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yunsheng Lin <linyunsheng@...wei.com>,
        Guillaume Nault <gnault@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        linux-rdma@...r.kernel.org, bpf <bpf@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        Andrew Lunn <andrew@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
        Sven Auhagen <sven.auhagen@...eatech.de>
Subject: Re: [PATCH net-next v4 1/4] mm: add a signature in struct page

On Tue, 11 May 2021 at 17:19, Matthew Wilcox <willy@...radead.org> wrote:
>
> On Tue, May 11, 2021 at 05:11:13PM +0300, Ilias Apalodimas wrote:
> > Hi Matthew,
> >
> > On Tue, May 11, 2021 at 02:45:32PM +0100, Matthew Wilcox wrote:
> > > On Tue, May 11, 2021 at 03:31:15PM +0200, Matteo Croce wrote:
> > > > @@ -101,6 +101,7 @@ struct page {
> > > >                    * 32-bit architectures.
> > > >                    */
> > > >                   unsigned long dma_addr[2];
> > > > +                 unsigned long signature;
> > > >           };
> > > >           struct {        /* slab, slob and slub */
> > > >                   union {
> > >
> > > No.  Signature now aliases with page->mapping, which is going to go
> > > badly wrong for drivers which map this page into userspace.
> > >
> > > I had this as:
> > >
> > > +                       unsigned long pp_magic;
> > > +                       unsigned long xmi;
> > > +                       unsigned long _pp_mapping_pad;
> > >                         unsigned long dma_addr[2];
> > >
> > > and pp_magic needs to be set to something with bits 0&1 clear and
> > > clearly isn't a pointer.  I went with POISON_POINTER_DELTA + 0x40.
> >
> > Regardless to the changes required, there's another thing we'd like your
> > opinion on.
> > There was a change wrt to the previous patchset. We used to store the
> > struct xdp_mem_info into page->private.  On the new version we store the
> > page_pool ptr address in page->private (there's an explanation why on the
> > mail thread, but the tl;dr is that we can get some more speed and keeping
> > xdp_mem_info is not that crucial). So since we can just store the page_pool
> > address directly, should we keep using page->private or it's better to
> > do:
> >
> > +                       unsigned long pp_magic;
> > +                       unsigned long pp_ptr;
> > +                       unsigned long _pp_mapping_pad;
> >                         unsigned long dma_addr[2];
> > and use pp_ptr?
>
> I'd rather you didn't use page_private ... Any reason not to use:
>
>                         unsigned long pp_magic;
>                         struct page_pool *pp;
>                         unsigned long _pp_mapping_pad;
>                         unsigned long dma_addr[2];
>
> ?

Nope not at all, either would work. we'll switch to that