linux-kernel - Re: [PATCH 2/3] socket: Rename SO_RCVTIMEO/ SO_SNDTIMEO with

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Date:   Tue, 8 Jan 2019 13:19:05 -0800
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        ccaulfie@...hat.com, Helge Deller <deller@....de>,
        Paul Mackerras <paulus@...ba.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Richard Henderson <rth@...ddle.net>,
        cluster-devel <cluster-devel@...hat.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-alpha@...r.kernel.org,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-mips@...r.kernel.org,
        Parisc List <linux-parisc@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>
Subject: Re: [PATCH 2/3] socket: Rename SO_RCVTIMEO/ SO_SNDTIMEO with _OLD suffixes

On Tue, Jan 8, 2019 at 12:04 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Tue, Jan 8, 2019 at 6:24 AM Deepa Dinamani <deepa.kernel@...il.com> wrote:
> >
> > SO_RCVTIMEO and SO_SNDTIMEO socket options use struct timeval
> > as the time format. struct timeval is not y2038 safe.
> > The subsequent patches in the series add support for new socket
> > timeout options with _NEW suffix that are y2038 safe.
> > Rename the existing options with _OLD suffix forms so that the
> > right option is enabled for userspace applications according
> > to the architecture and time_t definition of libc.
> >
> > Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
>
> Looks good overall. A few minor concerns:
>
> The description above makes it sound like there is a bug with y2038-safety
> in this particular interface, which I think is just not what you meant,
> as the change is only needed for compatiblity with new C libraries
> that work around the y2038 problem in general by changing their
> timeval definition.

Right, there is y2038 safety issue, just the libc part that needs to be handled.
I will fix the commit text.

> > diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
> > index 76976d6e50f9..c98ad9777ad9 100644
> > --- a/fs/dlm/lowcomms.c
> > +++ b/fs/dlm/lowcomms.c
> > @@ -1089,12 +1089,12 @@ static void sctp_connect_to_sock(struct connection *con)
> >          * since O_NONBLOCK argument in connect() function does not work here,
> >          * then, we should restore the default value of this attribute.
> >          */
> > -       kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&tv,
> > +       kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO_OLD, (char *)&tv,
> >                           sizeof(tv));
> >         result = sock->ops->connect(sock, (struct sockaddr *)&daddr, addr_len,
> >                                    0);
> >         memset(&tv, 0, sizeof(tv));
> > -       kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&tv,
> > +       kernel_setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO_OLD, (char *)&tv,
> >                           sizeof(tv));
> >
> >         if (result == -EINPROGRESS)
>
> It took me a bit to realize there that this is safe as well even if
> we don't use SO_SNDTIMEO_NEW, for the same reason.

Correct.

> > --- a/net/compat.c
> > +++ b/net/compat.c
> > @@ -378,7 +378,7 @@ static int compat_sock_setsockopt(struct socket *sock, int level, int optname,
> >                 return do_set_attach_filter(sock, level, optname,
> >                                             optval, optlen);
> >         if (!COMPAT_USE_64BIT_TIME &&
> > -           (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO))
> > +           (optname == SO_RCVTIMEO_OLD || optname == SO_SNDTIMEO_OLD))
> >                 return do_set_sock_timeout(sock, level, optname, optval, optlen);
> >
> >         return sock_setsockopt(sock, level, optname, optval, optlen);
> > @@ -450,7 +450,7 @@ static int compat_sock_getsockopt(struct socket *sock, int level, int optname,
> >                                 char __user *optval, int __user *optlen)
> >  {
> >         if (!COMPAT_USE_64BIT_TIME &&
> > -           (optname == SO_RCVTIMEO || optname == SO_SNDTIMEO))
> > +           (optname == SO_RCVTIMEO_OLD || optname == SO_SNDTIMEO_OLD))
> >                 return do_get_sock_timeout(sock, level, optname, optval, optlen);
> >         return sock_getsockopt(sock, level, optname, optval, optlen);
> >  }
>
> I looked at the original code and noticed that it's horrible, which of course
> is not your fault, but I wonder if we should just fix it now to avoid that
> get_fs()/set_fs() hack, since that code mostly implements what you
> also have in your patch 3 (which is done more nicely).

I did think of getting rid of set_fs()/ get_fs() here.
But, I wasn't sure as the maintainers seemed to prefer to leave to the
old code as is in the other series for timestamps.

> I'll follow up with a patch to demonstrate what I mean here. Your third
> patch will then just have to add another code path so we can handle
> all of old_timespec32 (for existing 32-bit user space), __kernel_old_timespec
> (for sparc64) and __kernel_sock_timeval (for everything else).

Cool, I will rebase on top of your patch.

Thanks,
Deepa