netdev - Re: [PATCH v4 2/4] net: socket: rework SIOC?IFMAP ioctls

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: <CAK8P3a08F1Xk2Vz69CUN=sJcBkqZvcrkd06qrmG3SMR8VhBN4A@mail.gmail.com>
Date:   Tue, 24 Nov 2020 20:05:46 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 2/4] net: socket: rework SIOC?IFMAP ioctls

On Tue, Nov 24, 2020 at 5:13 PM David Laight <David.Laight@...lab.com> wrote:
>
> From: Arnd Bergmann
> > Sent: 24 November 2020 15:18
> >
> > SIOCGIFMAP and SIOCSIFMAP currently require compat_alloc_user_space()
> > and copy_in_user() for compat mode.
> >
> > Move the compat handling into the location where the structures are
> > actually used, to avoid using those interfaces and get a clearer
> > implementation.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> > changes in v3:
> >  - complete rewrite
> ...
> >  include/linux/compat.h | 18 ++++++------
> >  net/core/dev_ioctl.c   | 64 +++++++++++++++++++++++++++++++++---------
> >  net/socket.c           | 39 ++-----------------------
> >  3 files changed, 62 insertions(+), 59 deletions(-)
> >
> > diff --git a/include/linux/compat.h b/include/linux/compat.h
> > index 08dbd34bb7a5..47496c5eb5eb 100644
> > --- a/include/linux/compat.h
> > +++ b/include/linux/compat.h
> > @@ -96,6 +96,15 @@ struct compat_iovec {
> >       compat_size_t   iov_len;
> >  };
> >
> > +struct compat_ifmap {
> > +     compat_ulong_t mem_start;
> > +     compat_ulong_t mem_end;
> > +     unsigned short base_addr;
> > +     unsigned char irq;
> > +     unsigned char dma;
> > +     unsigned char port;
> > +};
>
> Isn't the only difference the number of pad bytes at the end?

No, the main difference is in the first two fields, which are
'unsigned long' and therefore different. The three-byte padding
is in fact the same on all architectures (including x86) that
have a compat mode, though it might be different on
m68k and arm-oabi, which have slightly special struct
alignment rules.

It could be done with two assignments and a memcpy, but
I like the individual assignments better here.

      Arnd