• Re: Bug#1054552: glibc: stat fails when access time is bogus

    From Aurelien Jarno@21:1/5 to Simon McVittie on Thu Oct 26 19:30:02 2023
    control: reassign -1 dpkg
    control: retitle -1 dpkg: stat fails on 32-bit systems when access time is bogus

    Hi,

    On 2023-10-25 23:29, Simon McVittie wrote:
    Control: reassign -1 libc6

    On Wed, 25 Oct 2023 at 20:53:57 +0200, Jarek Czekalski wrote:
    I tried to upgrade system (apt-get upgrade), but it failed in dpkg:

    Unpacking initscripts (3.06-4) over (2.96-7+deb11u1) ...
    dpkg: error processing archive /var/cache/apt/archives/initscripts_3.06-4_all.deb (--unpack):
     unable to stat './var/log' (which was about to be installed): Value too large for defined data type

    This is nothing to do with GLib (libglib2.0-0), but I assume you meant
    glibc (libc6)? Quoting the rest of the bug report below for glibc maintainers:

    stat /var/log

      File: /var/log
      Size: 4096            Blocks: 8          IO Block: 4096 directory
    Device: 8,1     Inode: 2752691     Links: 12
    Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/ root)
    Access: 2040-05-10 23:31:40.285032309 +0200
    Modify: 2023-10-25 16:03:42.313742411 +0200
    Change: 2023-10-25 16:03:42.313742411 +0200
     Birth: 2017-02-27 09:46:56.739719147 +0100

    This date (2040) causes dpkg to fail. The workaround is correcting it by touch /var/log.

    Running system with bogus date (2040).
       * What exactly did you do (or not do) that was effective (or
         ineffective)?
    touch /var/log
       * What was the outcome of this action?
    dpkg started working
       * What outcome did you expect instead?
    dpkg should work with strange date or give a better message. Maybe just documentation (for stat) should be fixed and suggest problems with dates.

    Current outcome is as follows: apt-get suddenly fails with a cryptic message
    (initially it was "unable to stat '.'" instead of /var/log). It may be extremely difficult to diagnose the issue.

    It is not possible for 32-bit stat() to work correctly on 32-bit systems
    with dates beyond 2038, because the timestamp will not fit in the data
    type used. The only solution would be for the program in question (in
    this case, dpkg) to be compiled with support for 64-bit timestamps.

    I agree with the explanation.

    Your bug report seems to be from an upgrade from Debian 11 to Debian 12,
    and Debian 11's glibc version did not support APIs that provide 64-bit timestamps on 32-bit systems, so Debian 11's dpkg cannot support that
    either.

    Debian 12's glibc does, but that will only help you after fully upgrading
    to Debian 12, at which point you will have Debian 12 versions of glibc
    and dpkg.

    Yes, and that also means there is nothing that can be done on the glibc
    side as the API is already provided started with Debian 12.

    Unfortunately, I don't think there's necessarily anything that can be done here, beyond the general move towards supporting 64-bit timestamps distribution-wide that is already in progress.

    The other alternative is to add support at the dpkg level, just like it
    is already the case for some packages like coreutils. I am therefore reassigning the bug to dpkg, but I fully understand if it get tagged as
    wontfix until 64-bit timestamps are supported at the distribution-wide
    level.

    Regards
    Aurelien

    --
    Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://aurel32.net

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  • From Guillem Jover@21:1/5 to Aurelien Jarno on Fri Oct 27 02:30:01 2023
    Hi!

    On Thu, 2023-10-26 at 19:27:48 +0200, Aurelien Jarno wrote:
    control: reassign -1 dpkg
    control: retitle -1 dpkg: stat fails on 32-bit systems when access time is bogus

    On 2023-10-25 23:29, Simon McVittie wrote:
    On Wed, 25 Oct 2023 at 20:53:57 +0200, Jarek Czekalski wrote:
    I tried to upgrade system (apt-get upgrade), but it failed in dpkg:

    Unpacking initscripts (3.06-4) over (2.96-7+deb11u1) ...
    dpkg: error processing archive /var/cache/apt/archives/initscripts_3.06-4_all.deb (--unpack):
     unable to stat './var/log' (which was about to be installed): Value too large for defined data type

    stat /var/log

      File: /var/log
      Size: 4096            Blocks: 8          IO Block: 4096 directory
    Device: 8,1     Inode: 2752691     Links: 12
    Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/ root)
    Access: 2040-05-10 23:31:40.285032309 +0200
    Modify: 2023-10-25 16:03:42.313742411 +0200
    Change: 2023-10-25 16:03:42.313742411 +0200
     Birth: 2017-02-27 09:46:56.739719147 +0100

    This date (2040) causes dpkg to fail. The workaround is correcting it by touch /var/log.

    It is not possible for 32-bit stat() to work correctly on 32-bit systems with dates beyond 2038, because the timestamp will not fit in the data
    type used. The only solution would be for the program in question (in
    this case, dpkg) to be compiled with support for 64-bit timestamps.

    I agree with the explanation.

    Your bug report seems to be from an upgrade from Debian 11 to Debian 12, and Debian 11's glibc version did not support APIs that provide 64-bit timestamps on 32-bit systems, so Debian 11's dpkg cannot support that either.

    Debian 12's glibc does, but that will only help you after fully upgrading to Debian 12, at which point you will have Debian 12 versions of glibc
    and dpkg.

    Unfortunately, I don't think there's necessarily anything that can be done here, beyond the general move towards supporting 64-bit timestamps distribution-wide that is already in progress.

    The other alternative is to add support at the dpkg level, just like it
    is already the case for some packages like coreutils. I am therefore reassigning the bug to dpkg, but I fully understand if it get tagged as wontfix until 64-bit timestamps are supported at the distribution-wide
    level.

    Right, I think this would be ideal, otherwise the entire port becomes
    pretty useless if dpkg itself cannot even be used. There are several
    things to take into account though:

    - autoconf with the AC_SYS_YEAR2038 macro has not been released yet,
    so I'll need to implement a replacement for that, which I guess I
    might need to do anyway otherwise that would involve requiring a
    too recent autoconf version.
    - This could wait for the time64 transition, but then this will
    leave the i386 port broken (as is supposed to be intended by
    that transition), which means this report could not be solved,
    but that seems less than ideal as I've mentioned before, because
    that means the port is dead at that point. So…
    - Building dpkg with time64 support *everywhere* could be a problem
    when the shared libraries it uses or it might use in the future are
    not also built with time64 support (the default for i386 based on
    the proposed time64 plan in Debian). I've done a brief check over
    all currently potentially used libraries and their public
    interfaces:
    + libmd → ok (no types involving time)
    + libselinux → ok
    + libz → ok
    + libbz2 → ok
    + liblzma → ok
    + libzstd → ok
    + libps → Hurd library, might be a problem, need to check further
    + libsocket → Solaris library (not relevant in Debian)
    + libkvm → BSD library (not relevant in Debian, several BSDs
    force-switched to time64 anyway)
    + libcurses → seems ok on a quick skim
    And prospective ones:
    + libaudit → ok
    + libacl → ok
    + libcap → ok
    - If none of these libraries get built with time64 on all 32-bit
    arches (including i386), then dpkg might still fail due to
    internal failures in those libraries.

    So I guess once the first part is done I _could_ build dpkg with time64
    on *all* 32-bit arches that support it (including i386), although if
    (like it looks like) the ABIs for the listed shared libraries are not
    affected by time64, then it might be way better to also build these
    libraries everywhere with time64 anyway, because that should not affect backwards compat for its current users, and if new symbols get added
    with time types then those would not affect old binary programs that
    people are concerned about, and would still make it safe to use the
    libraries.

    Thanks,
    Guillem

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