netdev - Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy

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Message-ID: <CAAeHK+yxcG=KBjG0A5BicBA7Zwu6LR6t=g5b-9EAPXA8_Dfm2g@mail.gmail.com>
Date:   Mon, 18 Mar 2019 14:16:54 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>,
        Kees Cook <keescook@...omium.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
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        Linux Memory Management List <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
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        "open list:KERNEL SELFTEST FRAMEWORK" 
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        Dave Martin <Dave.Martin@....com>,
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        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive

On Mon, Mar 18, 2019 at 2:14 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> On Fri, Mar 15, 2019 at 9:03 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> >
> >
> > On 03/15/2019 12:51 PM, Andrey Konovalov wrote:
> > > This patch is a part of a series that extends arm64 kernel ABI to allow to
> > > pass tagged user pointers (with the top byte set to something else other
> > > than 0x00) as syscall arguments.
> > >
> > > tcp_zerocopy_receive() uses provided user pointers for vma lookups, which
> > > can only by done with untagged pointers.
> > >
> > > Untag user pointers in this function.
> > >
> > > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > > ---
> > >  net/ipv4/tcp.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > > index 6baa6dc1b13b..89db3b4fc753 100644
> > > --- a/net/ipv4/tcp.c
> > > +++ b/net/ipv4/tcp.c
> > > @@ -1758,6 +1758,8 @@ static int tcp_zerocopy_receive(struct sock *sk,
> > >       int inq;
> > >       int ret;
> > >
> > > +     address = untagged_addr(address);
> > > +
> > >       if (address & (PAGE_SIZE - 1) || address != zc->address)
> >
> > The second test will fail, if the top bits are changed in address but not in zc->address
>
> Will fix in v12, thanks Eric!

Looking at the code, what's the point of this address != zc->address
check? Should I just remove it?

>
> >
> > >               return -EINVAL;
> > >
> > >
> >