linux-kernel - Re: [PATCH v2 4/5] pselect6: use __kernel

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Message-ID: <CABeXuvoOEW9+5BPiDN+2S1boyMSg+csvSAd4ue03TB+yEO6dLg@mail.gmail.com>
Date:   Sat, 15 Sep 2018 11:37:38 -0700
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        linux-aio <linux-aio@...ck.org>
Subject: Re: [PATCH v2 4/5] pselect6: use __kernel_timespec

On Sat, Sep 15, 2018 at 8:28 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Sat, Sep 15, 2018 at 7:09 AM Deepa Dinamani <deepa.kernel@...il.com> wrote:
>
> > +#if defined(CONFIG_64BIT_TIME)
> > +
> > +COMPAT_SYSCALL_DEFINE6(pselect6_time64, int, n, compat_ulong_t __user *, inp,
> > +       compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
> > +       struct __kernel_timespec __user *, tsp, void __user *, sig)
>
> I got a link error here since compat_sys_pselect6_time64 and
> compat_sys_ppoll_time64 are only defined when CONFIG_64BIT_TIME
> is set.
>
> I did not think we would select this symbol on arm64, is that a mistake
> on my side, or should the #ifdef check be removed?

But, this is a compat syscall.
When we introduced this CONFIG_64BIT_TIME we planned to use it for
compat syscalls also is my understanding.

config 64BIT_TIME
         def_bool ARCH_HAS_64BIT_TIME
         help
          This should be selected by all architectures that need to support
           new system calls with a 64-bit time_t. This is relevant on all 32-bit
           architectures, and 64-bit architectures as part of compat syscall
           handling.

This means it should be set on 64 bit architechtures also right?

If we don't have the #ifdef here then we have an entry point from
userspace defined and Thomas had pointed out that it was a security
hole.

-Deepa