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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Tue, 31 May 2022 10:24:15 +0200
Message-ID: <CAK8P3a0bmE03wJ_iELrAMyFvamwd_r5aLsFBH=6=5YaueO=-kg@mail.gmail.com>
Subject: Re: PROBLEM: with daemon.c after y2038 on 32-bits Kernel
To:     =?UTF-8?Q?Arnaud_Pana=C3=AFotis?= <arnaud.panaiotis@gmx.fr>
Cc:     linux-kernel@vger.kernel.org, y2038@lists.linaro.org,
        alpha@sourceware.org
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On 17/05/2022 09:51, Arnaud Pana=C3=AFotis wrote:
> Hello,
>
> I'm working for a client to generate embedded 32-bits Linux Kernel workin=
g after y2038 issue.
>
> I generated a 5.15 Kernel thought Buildroot with Coreutils 9.0, GCC 11.2.=
0, Binutils 2.37, Glibc 2.34-9 and CFLAGS  -D_LARGEFILE_SOURCE -D_FILE_OFFS=
ET_BITS=3D64  -D_TIME_BITS=3D64.
>
> I encounter an issue while working with OpenSSH (I initially contacted th=
em before).

To clarify: did you build just openssh with  -D_TIME_BITS=3D64, or did
you build the user space
this way?

> After 2038, /usr/sbin/sshd does not create an error but it child does gen=
erate this one:
> daemon() failed: Value too large for defined data type
>
> This happend here in sshd.c:
>
> 2019         /*
> 2020          * If not in debugging mode, not started from inetd and not =
already
> 2021          * daemonized (eg re-exec via SIGHUP), disconnect from the c=
ontrolling
> 2022          * terminal, and fork.  The original process exits.
> 2023          */
> 2024         already_daemon =3D daemonized();
> 2025         if (!(debug_flag || inetd_flag || no_daemon_flag || already_=
daemon)) {
> 2026
> 2027                 if (daemon(0, 0) =3D=3D -1)
> 2028                         fatal("daemon() failed: %.200s", strerror(er=
rno));

My guess is that there are parts of glibc that are not fully
y2038-safe at the moment, but
merely provide the interfaces for time64 applications.


In the glibc code, I see

int
daemon (int nochdir, int noclose)
{
...
                if ((fd =3D __open_nocancel(_PATH_DEVNULL, O_RDWR, 0)) !=3D=
 -1
                    && (__builtin_expect (__fstat64 (fd, &st), 0)
                        =3D=3D 0)) {
...
                             } else {
                        __close_nocancel_nostatus (fd);
                        return -1;
                }
     return (0);
}

__fstatat64 (int fd, const char *file, struct stat64 *buf, int flags)
{
  struct __stat64_t64 st_t64;
  return __fstatat64_time64 (fd, file, &st_t64, flags)
         ?: __cp_stat64_t64_stat64 (&st_t64, buf);
}

If I'm reading this correctly, daemon() internally uses the time32
version of 'stat', which
fails for files with out-of-range timestamps. Are you able to rebuild
the ssh binary
(or your entire distro, if that's easier) against musl-1.2.x instead
of glibc to see if the
same thing happens there?

       Arnd

> To reproduce:
>
> # date -s "2040-05-12"
> # hwclock --systohc
> # reboot
> # /usr/sbin/sshd
>
> Note this error occurs only after the reboot, and setting a date before 2=
038 also require a reboot to remove the error.
>
> strace and gdb trace linked.
>
> Let me know if you need additional information.