linux-kernel - Re: [-next] strace tests fail because of "y2038: socket: Add compat_sys_recvmmsg

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Date:   Tue, 18 Dec 2018 08:56:53 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [-next] strace tests fail because of "y2038: socket: Add
 compat_sys_recvmmsg_time64"

On Mon, Dec 17, 2018 at 11:05:06PM +0100, Arnd Bergmann wrote:
> On Mon, Dec 17, 2018 at 10:40 PM Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Mon, Dec 17, 2018 at 2:06 PM Heiko Carstens
> > <heiko.carstens@...ibm.com> wrote:
> > >
> > > Hi Arnd,
> > >
> > > in linux-next as of today 16 strace self tests fail on s390. I could
> > > bisect this to b136972b063b ("y2038: socket: Add compat_sys_recvmmsg_time64").
> > >
> > > The following tests fail:
> >
> > Hi Heiko,
> >
> > Thanks for the report and sorry I broke things. I'll have a closer look
> > tomorrow if I don't find it right away. I suppose the regression was in
> > native system calls, not the compat syscalls with 31-bit user space,
> > right?

Yes, I was talking about 64 bit native system calls.

> I found a bug in my patch by inspection. Can you try if the patch
> below makes it all work (apologies for the garbled whitespace),
> I'm considering a rewrite of that function now (to split it into two
> again), but want to make sure there isn't another problem in my
> original patch.

With your patch below applied, the tests pass again.

Thanks!

> ----
> diff --git a/net/socket.c b/net/socket.c
> index 3bb2ee083f97..7f9f225d0b6c 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2486,12 +2486,12 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg,
>          return -EFAULT;
> 
>      if (!timeout && !timeout32)
> -        do_recvmmsg(fd, mmsg, vlen, flags, NULL);
> +        return do_recvmmsg(fd, mmsg, vlen, flags, NULL);
> 
>      datagrams = do_recvmmsg(fd, mmsg, vlen, flags, &timeout_sys);
> 
> -    if (!datagrams)
> -        return 0;
> +    if (datagrams <= 0)
> +        return datagrams;
> 
>      if (timeout && put_timespec64(&timeout_sys, timeout))
>          datagrams = -EFAULT;
>