linux-kernel - Re: PROBLEM: with daemon.c after y2038 on 32-bits Kernel

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Message-ID: <cbde441f-b172-2a01-606d-0f97681a59fb@gmx.fr>
Date:   Tue, 31 May 2022 14:16:58 +0200
From:   Arnaud Panaïotis <arnaud.panaiotis@....fr>
To:     Adhemerval Zanella <adhemerval.zanella@...aro.org>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     y2038@...ts.linaro.org, libc-alpha@...rceware.org,
        linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: with daemon.c after y2038 on 32-bits Kernel

Hello,

On 31/05/2022 12:54, Adhemerval Zanella wrote:
>
> On 31/05/2022 05:33, Arnd Bergmann via Libc-alpha wrote:
>> (cc correct libc-alpha list, sorry for the typo)
>>
>> On Tue, May 31, 2022 at 10:24 AM Arnd Bergmann <arnd@...nel.org> wrote:
>>> On 17/05/2022 09:51, Arnaud Panaïotis wrote:
>>>> I'm working for a client to generate embedded 32-bits Linux Kernel working 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_OFFSET_BITS=64  -D_TIME_BITS=64.
>>>>
>>>> I encounter an issue while working with OpenSSH (I initially contacted them before).
>>> To clarify: did you build just openssh with  -D_TIME_BITS=64, or did
>>> you build the entire user space this way?

I made a patch for the whole Builroot, this way all packages are built
with it (unless it is filter-out, I had to make few patches).

Option is present in build log for daemon.c and sshd.c

>>>
>>>> After 2038, /usr/sbin/sshd does not create an error but it child does generate 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 controlling
>>>> 2022          * terminal, and fork.  The original process exits.
>>>> 2023          */
>>>> 2024         already_daemon = daemonized();
>>>> 2025         if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) {
>>>> 2026
>>>> 2027                 if (daemon(0, 0) == -1)
>>>> 2028                         fatal("daemon() failed: %.200s", strerror(errno));
>>> 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 = __open_nocancel(_PATH_DEVNULL, O_RDWR, 0)) != -1
>>>                      && (__builtin_expect (__fstat64 (fd, &st), 0)
>>>                          == 0)) {
>>> ...
>>>                               } else {
>>>                          __close_nocancel_nostatus (fd);
>>>                          return -1;
>>>                  }
>>>       return (0);
>>> }
> Thanks for catching it, I have opened a bug report for it [1] and I will fix
> and backport to 2.34 and 2.35.
>
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=29203
Thanks, I'll watch this.
>
>>> __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?

Musl did not worked previously for me, not sure for openssh only within
Buildroot.

I'll test the patch from ticket 29203, probably the easiest solution for me.

>>>
>>>         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 2038 also require a reboot to remove the error.
>>>>
>>>> strace and gdb trace linked.
>>>>
>>>> Let me know if you need additional information.
--

*Arnaud PANAÏOTIS* | Lead Developer Freelance
+33 6 34 82 12 62 | arnaud.panaiotis@....fr <mailto:Arnaud Panaïotis
<arnaud.panaiotis@....fr>>

18 place Jean Moulin - 38000 Grenoble
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