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    SubjectRe: [PATCH 2/3] socket: Rename SO_RCVTIMEO/ SO_SNDTIMEO with _OLD suffixes
    On Tue, Jan 8, 2019 at 6:24 AM Deepa Dinamani <deepa.kernel@gmail.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@gmail.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.

    > 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.

    > --- 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'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).

    Arnd

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