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

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Message-ID: <4b83ea18-e106-e7ec-d1d9-daa74aeaf990@linaro.org>
Date:   Tue, 31 May 2022 07:54:43 -0300
From:   Adhemerval Zanella <adhemerval.zanella@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>,
        Arnaud Panaïotis <arnaud.panaiotis@....fr>
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



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?
>>
>>> 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

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