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Setting $) where /proc is not available on Linux returns an error #13322

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p5pRT opened this issue Oct 1, 2013 · 3 comments
Open

Setting $) where /proc is not available on Linux returns an error #13322

p5pRT opened this issue Oct 1, 2013 · 3 comments
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distro-Linux type-core

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@p5pRT
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p5pRT commented Oct 1, 2013

Migrated from rt.perl.org#120057 (status was 'open')

Searchable as RT120057$
@p5pRT
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p5pRT commented Oct 1, 2013

From @stephane-chazelas

Created by @stephane-chazelas

$ perl -le 'chroot("/tmp"); $! = 0; $) = 1000; print "$!"'
No such file or directory

I think (from running under strace) that's because perl tries to open
/proc/sys/kernel/ngroups_max (possibly as part of a getconf()) which
here is not available.

Though I can understand that not finding that file may be considered an
error, IMO, it should be documented, and maybe an alternative way to
check whether it succeeded or not should be documented.

I observe it on Debian sid now and debian wheezy (v5.14.2), not
on ubuntu 10.04 (v5.10.1).

Note that when you try to set $) to more than ngroups_max groups, perl
doesn't issue a warning nor set $! to an error (which possibly has
security implications).

Perl Info 

Flags:
    category=core
    severity=low

Site configuration information for perl 5.18.1:

Configured by Debian Project at Thu Sep 12 00:36:36 UTC 2013.

Summary of my perl5 (revision 5 version 18 subversion 1) configuration:
   
  Platform:
    osname=linux, osvers=3.2.0-4-amd64, archname=x86_64-linux-gnu-thread-multi
    uname='linux babin 3.2.0-4-amd64 #1 smp debian 3.2.46-1+deb7u1 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Dldflags= -Wl,-z,relro -Dlddlflags=-shared -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.18 -Darchlib=/usr/lib/perl/5.18 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.18.1 -Dsitearch=/usr/local/lib/perl/5.18.1 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Uversiononly -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.18.1 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.8.1', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.18.1
    gnulibc_version='2.17'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
    DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
    DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: Set location of libperl.a to /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
    DEBPKG:debian/prefix_changes - Fiddle with *PREFIX and variables written to the makefile
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/module_build_man_extensions - http://bugs.debian.org/479460 Adjust Module::Build manual page extensions for the Debian Perl policy
    DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
    DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038] http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
    DEBPKG:debian/cpanplus_definstalldirs - http://bugs.debian.org/533707 Configure CPANPLUS to use the site directories by default.
    DEBPKG:debian/cpanplus_config_path - Save local versions of CPANPLUS::Config::System into /etc/perl.
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/702096 Point users to Debian packages of deprecated core modules
    DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the upstream Git repository
    DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.18.1-4 in patchlevel.h
    DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl #96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
    DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
    DEBPKG:debian/hurd_test_todo_syslog - http://bugs.debian.org/650093 Disable failing GNU/Hurd tests in cpan/Sys-Syslog/t/syslog.t
    DEBPKG:debian/hurd_test_skip_sigdispatch - http://bugs.debian.org/650188 Disable failing GNU/Hurd tests op/sigdispatch.t
    DEBPKG:debian/hurd_test_skip_stack - http://bugs.debian.org/650175 Disable failing GNU/Hurd tests dist/threads/t/stack.t
    DEBPKG:debian/hurd_test_skip_pipe - http://bugs.debian.org/650187 Disable failing GNU/Hurd tests io/pipe.t
    DEBPKG:debian/hurd_test_skip_io_pipe - http://bugs.debian.org/650096 Disable failing GNU/Hurd tests dist/IO/t/io_pipe.t
    DEBPKG:fixes/manpage_name_Test-Harness - http://bugs.debian.org/650451 [rt.cpan.org #73399] cpan/Test-Harness: add NAME headings in modules with POD
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/660195 [rt.cpan.org #28632] Make EU::MM pass LD through to recursive Makefile.PL invocations
    DEBPKG:debian/perl5db-x-terminal-emulator.patch - http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs - http://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
    DEBPKG:debian/hurd_net_ping_disable_test - http://bugs.debian.org/709385 Disable failing Net-Ping tests for GNU/Hurd
    DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790] http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore' option not respected
    DEBPKG:fixes/net_ftp_failed_command - [rt.cpan.org #37700] http://bugs.debian.org/491062 Net::FTP: cope gracefully with a failed command
    DEBPKG:fixes/perlbug-patchlist - [3541c11] http://bugs.debian.org/710842 [perl #118433] Make perlbug look up the list of local patches at run time
    DEBPKG:fixes/regexp-preserve - http://bugs.debian.org/718209 [perl #118213] [f4194b2] RT #118213: handle $r=qr/.../; /$r/p properly
    DEBPKG:fixes/regexp-preserve-testcases - http://bugs.debian.org/718209 [perl #118213] [4d7b2f5] Disable new //p tests
    DEBPKG:fixes/module_metadata_security_doc - [68cdd4b] CVE-2013-1437 documentation fix
    DEBPKG:fixes/module_metadata_taint_fix - [bff978f] http://bugs.debian.org/722210 [rt.cpan.org #88576] untaint version, if needed, in Module::Metadata


@INC for perl 5.18.1:
    /etc/perl
    /usr/local/lib/perl/5.18.1
    /usr/local/share/perl/5.18.1
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.18
    /usr/share/perl/5.18
    /usr/local/lib/site_perl
    .


Environment for perl 5.18.1:
    HOME=/home/stephane
    LANG=en_GB.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/sbin:/usr/sbin:/usr/local/sbin:/home/stephane/bin
    PERL_BADLANG (unset)
    SHELL=/bin/zsh

@p5pRT
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p5pRT commented Oct 2, 2013

From @Leont

On Tue, Oct 1, 2013 at 12​:16 PM, stephane.chazelas@​gmail.com <
perlbug-followup@​perl.org> wrote​:

$ perl -le 'chroot("/tmp"); $! = 0; $) = 1000; print "$!"'
No such file or directory

But what is the value of $) afterwards? The fact that $! is set does not
necessarily mean the 'assignment' failed. $! is only specified after a
failed operation, but the magic ID variables don't signal success/failure
in any way. Worse yet, $) does two things at a time (setgroups(2) and
setegid(2)), making this even more troublesome.

I think (from running under strace) that's because perl tries to open

/proc/sys/kernel/ngroups_max (possibly as part of a getconf()) which
here is not available.

Though I can understand that not finding that file may be considered an
error, IMO, it should be documented, and maybe an alternative way to
check whether it succeeded or not should be documented.

It uses a compile-time value for ngroup_max if it can't establish a better
value at runtime. This is rather sensible.

I observe it on Debian sid now and debian wheezy (v5.14.2), not
on ubuntu 10.04 (v5.10.1).

Probably sysconf(3)'s implementation changed in the mean time.

Note that when you try to set $) to more than ngroups_max groups, perl
doesn't issue a warning nor set $! to an error (which possibly has
security implications).

Yeah, superfluous groups are currently ignored. I'm not sure this is
sensible behavior either.

Leon

@p5pRT
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p5pRT commented Oct 2, 2013

The RT System itself - Status changed from 'new' to 'open'

@xenu xenu removed the affects-5.18 label Nov 19, 2021
@xenu xenu removed the Severity Low label Dec 29, 2021
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