[Bug libc/26401] New: Regressons in lchmod and fchmodat when /proc is not mounted

[Bug libc/26401] New: Regressons in lchmod and fchmodat when /proc is not mounted

[ldv at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

            Bug ID: 26401
           Summary: Regressons in lchmod and fchmodat when /proc is not
                    mounted
           Product: glibc
           Version: 2.32
               URL: https://sourceware.org/pipermail/libc-alpha/2020-July/
                    116512.html
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: ldv at sourceware dot org
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---
             Flags: security-

Fixes for https://sourceware.org/bugzilla/show_bug.cgi?id=14578
introduced regressions in cases when /proc is not mounted:
- lchmod used to return ENOSYS, now it returns EOPNOTSUPP;
- fchmodat(AT_SYMLINK_NOFOLLOW) used to return ENOTSUP, now it returns
EOPNOTSUPP which is different from ENOTSUP on some architectures, e.g. hppa.

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[ldv at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Dmitry V. Levin <ldv at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Regressons in lchmod and    |Regressions in lchmod and
                   |fchmodat when /proc is not  |fchmodat when /proc is not
                   |mounted                     |mounted

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[alkisg at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Alkis Georgopoulos <alkisg at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alkisg at gmail dot com

--- Comment #1 from Alkis Georgopoulos <alkisg at gmail dot com> ---
Hello, just noting that rsync in Ubuntu 20.10 is affected by this glibc issue:

https://bugs.launchpad.net/ubuntu/+source/rsync/+bug/1902109
https://github.com/WayneD/rsync/issues/109

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[tom at compton dot nu]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Tom Hughes <tom at compton dot nu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tom at compton dot nu

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[tom at compton dot nu]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

--- Comment #2 from Tom Hughes <tom at compton dot nu> ---
Also rsync in Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=1894485

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[arekm at maven dot pl]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Arkadiusz Miskiewicz <arekm at maven dot pl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |arekm at maven dot pl

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[adhemerval.zanella at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |adhemerval.zanella at linaro dot o
                   |                            |rg

--- Comment #3 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
I think there is no much glibc can do without proper kernel support [1].

[1] https://sourceware.org/pipermail/libc-alpha/2020-July/116513.html

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[ldv at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

--- Comment #4 from Dmitry V. Levin <ldv at sourceware dot org> ---
Just letting you know that we reverted commit
6b89c385d8bd0700b25bac2c2d0bebe68d5cc05d in our glibc build shortly after
reporting this issue.

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[Bug libc/26401] Regressions in lchmod and fchmodat when /proc is not mounted

[adhemerval.zanella at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26401

--- Comment #5 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
(In reply to Dmitry V. Levin from comment #4)
> Just letting you know that we reverted commit
> 6b89c385d8bd0700b25bac2c2d0bebe68d5cc05d in our glibc build shortly after
> reporting this issue.

Reading rsync bug report, I really think that EOPNOTSUPP is the correct error
code to return in this case. The configure was done on a build system where
lchmod does work (since it has procps mounted). So I do not fully agree this
really characterizes as a regression.

And I don't think reverting lchmod support since propcs might be not available
is the correct approach, best option would try to ask kernel to have proper
syscall support which does not require userland hacks. Rick Felker already sent
a patch, but it seems to be stuck.

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