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

Tue May 31 09:02:28 GMT 2022

Hello

On 31/05/2022 10:33, Arnd Bergmann wrote:
> (cc correct libc-alpha list, sorry for the typo)
>
> On Tue, May 31, 2022 at 10:24 AM Arnd Bergmann<arnd@kernel.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'm using Buildroot, I added it to TARGET_CPPFLAGS (also used by
TARGET_CLAGS) and HOST_CPPFLAGS (used by HOST_CFLAGS) in
buildroot/package/Makefile.in

Then all packages are built with the option (unless the package filter
it out, I had to create patches for few of them).

Extracts of logs while rebuild openssh:

/home/arnaud/devenv/branches/kernel510/output/host/bin/i686-buildroot-linux-gnu-gcc
  -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64  -Os -g0
-D_FORTIFY_SOURCE=1 -pipe -Wno-error=format-truncation -Wall -Wextra
-Wpointer-arith
  -Wuninitialized -Wsign-compare -Wformat-security
-Wsizeof-pointer-memaccess -Wno-pointer-sign -Wno-unused-parameter
-Wno-unused-result -Wimplicit-fallthrough -fno-strict-aliasing -ftrapv
-fno-builtin-memset -fstack-protector-strong   -fPIC -I. -I.. -I. -I./..
  -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
-D_XOPEN_SOURCE=600 -D_BSD_SOURCE -D_DEFAULT_SOURCE -DHAVE_CONFIG_H -c
daemon.c

/home/arnaud/devenv/branches/kernel510/output/host/bin/i686-buildroot-linux-gnu-gcc
  -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64  -Os -g0
-D_FORTIFY_SOURCE=1 -pipe -Wno-error=format-truncation -Wall -Wextra
-Wpointer-arith
  -Wuninitialized -Wsign-compare -Wformat-security
-Wsizeof-pointer-memaccess -Wno-pointer-sign -Wno-unused-parameter
-Wno-unused-result -Wimplicit-fallthrough -fno-strict-aliasing -ftrapv
-fno-builtin-memset -fstack-protector-strong -fPIE   -I. -I.
-D_LARGEFILE_SOURCE
  -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 -D_XOPEN_SOURCE=600
-D_BSD_SOURCE -D_DEFAULT_SOURCE -DSSHDIR=\"/etc/ssh\"
-D_PATH_SSH_PROGRAM=\"/usr/bin/ssh\"
-D_PATH_SSH_ASKPASS_DEFAULT=\"/usr/libexec/ssh-askpass\"
-D_PATH_SFTP_SERVER=\"/usr/libexec/sftp-server\"
  -D_PATH_SSH_KEY_SIGN=\"/usr/libexec/ssh-keysign\"
-D_PATH_SSH_PKCS11_HELPER=\"/usr/libexec/ssh-pkcs11-helper\"
-D_PATH_SSH_SK_HELPER=\"/usr/libexec/ssh-sk-helper\"
-D_PATH_SSH_PIDDIR=\"/var/run\"
-D_PATH_PRIVSEP_CHROOT_DIR=\"/var/empty\" -DHAVE_CONFIG_H -c
  sshd.c -o sshd.o

>>
>>> 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);
>> }
>>
>> __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?
I'd tried previously to build the entire distro with musl without
success, not sure I can do it only for openssh.
>>
>>         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@gmx.fr <mailto:Arnaud Panaïotis
<arnaud.panaiotis@gmx.fr>>

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