[perl #41344] setuid perl: "Setuid script changed" error when root cannot access directory

On Thu Jan 25 09:15:39 2007, varhus@seas.upenn.edu wrote:
> 
> This is a bug report for perl from varhus@seas.upenn.edu,
> generated with the help of perlbug 1.35 running under perl v5.8.8.
> 
> 
> -----------------------------------------------------------------
> [Please enter your report here]
> 
> If root cannot access the directory containing a setuid Perl script,
> running the setuid script fails with the misleading error "Setuid
> script changed".  This can happen when, for example, the setuid script
> is on an NFS filesystem mounted from a server which exported it with
> what Linux calls the "root_squash" option.
> 
> Both the original and target user can access the script, but suidperl
> tries to run several checks as root before doing seteuid() to the
> target user.  The one that fails is this block:
> 
>             Stat_t tmpstatbuf;
>             if (PerlLIO_stat(CopFILE(PL_curcop),&tmpstatbuf) < 0 ||
>                 tmpstatbuf.st_dev != PL_statbuf.st_dev ||
>                 tmpstatbuf.st_ino != PL_statbuf.st_ino) {
>                 Perl_croak(aTHX_ "Setuid script changed\n");
>             }
> 
> Since root doesn't have permission to search the directory containing
> the script, the stat() fails with an EACCES error.  It seems to me
> that it would be safe to move this check to after the point at which
> suidperl does seteuid() later on, rather than doing it as root.
> 
> Alternatively, it would be useful to not give this misleading error
> message.  I realize that the comment right above the check says that
> this is where we must "lie" about return status.  However, giving
> a better error message if stat() returns an EACCES error wouldn't
> seem to be giving extra information away, and would have saved me
> a lot of time trying to understand why Perl thought the script was
> changing when it clearly wasn't.  Plus, this error message isn't
> documented in perldiag.
> 
> [Please do not change anything below this line]
> -----------------------------------------------------------------
> ---
> Flags:
>     category=core
>     severity=low
> ---
> This perlbug was built using Perl v5.8.8 - Sun Apr 23 00:25:53 UTC
>    2006
> It is being executed now by  Perl v5.8.8 - Sun Apr 23 00:20:53 UTC
>    2006.
> 
> Site configuration information for perl v5.8.8:
> 
> Configured by abuild at Sun Apr 23 00:20:53 UTC 2006.
> 
> Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
>   Platform:
>     osname=linux, osvers=2.6.16, archname=i586-linux-thread-multi
>     uname='linux tait 2.6.16 #1 smp tue mar 14 18:04:33 utc 2006 i686
>    i686 i386 gnulinux '
>     config_args='-ds -e -Dprefix=/usr -Dvendorprefix=/usr
>    -Dinstallusrbinperl -Dusethreads -Di_db -Di_dbm -Di_ndbm -Di_gdbm
>    -Duseshrplib=true -Doptimize=-O2 -march=i586 -mtune=i686
>    -fmessage-length=0 -Wall -D_FORTIFY_SOURCE=2 -g -Wall -pipe'
>     hint=recommended, useposix=true, d_sigaction=define
>     usethreads=define use5005threads=undef useithreads=define
>    usemultiplicity=define
>     useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
>     use64bitint=undef use64bitall=undef uselongdouble=undef
>     usemymalloc=n, bincompat5005=undef
>   Compiler:
>     cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS
>    -DDEBUGGING -fno-strict-aliasing -pipe
>    -Wdeclaration-after-statement -D_LARGEFILE_SOURCE
>    -D_FILE_OFFSET_BITS=64',
>     optimize='-O2 -march=i586 -mtune=i686 -fmessage-length=0 -Wall
>    -D_FORTIFY_SOURCE=2 -g -Wall -pipe',
>     cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS
>    -DDEBUGGING -fno-strict-aliasing -pipe
>    -Wdeclaration-after-statement'
>     ccversion='', gccversion='4.1.0 (SUSE Linux)', gccosandvers=''
>     intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
>     d_longlong=define, longlongsize=8, d_longdbl=define,
>    longdblsize=12
>     ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
>    lseeksize=8
>     alignbytes=4, prototype=define
>   Linker and Libraries:
>     ld='cc', ldflags =''
>     libpth=/lib /usr/lib /usr/local/lib
>     libs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
>     perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
>     libc=/lib/libc-2.4.so, so=so, useshrplib=true, libperl=libperl.so
>     gnulibc_version='2.4'
>   Dynamic Linking:
>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E
>    -Wl,-rpath,/usr/lib/perl5/5.8.8/i586-linux-thread-multi/CORE'
>     cccdlflags='-fPIC', lddlflags='-shared'
> 
> Locally applied patches:
> 
> 
> ---
> @INC for perl v5.8.8:
>     /usr/lib/perl5/5.8.8/i586-linux-thread-multi
>     /usr/lib/perl5/5.8.8
>     /usr/lib/perl5/site_perl/5.8.8/i586-linux-thread-multi
>     /usr/lib/perl5/site_perl/5.8.8
>     /usr/lib/perl5/site_perl
>     /usr/lib/perl5/vendor_perl/5.8.8/i586-linux-thread-multi
>     /usr/lib/perl5/vendor_perl/5.8.8
>     /usr/lib/perl5/vendor_perl
>     .
> 
> ---
> Environment for perl v5.8.8:
>     HOME=/home1/v/varhus
>     LANG=en_US
>     LANGUAGE (unset)
>     LD_LIBRARY_PATH (unset)
>     LOGDIR (unset)
>    
PATH=/home1/v/varhus/bin:/pkg/openssh/bin:/pkg/k/krb5/bin:/usr/local/bin:/usr/bin:/usr/X11R6/bin:/bin:/usr/games:/opt/gnome/bin:/opt/kde3/bin:/usr/lib/mit/bin:/usr/lib/mit/sbin:/usr/lib/qt3/bin:/sbin:/usr/sbin:/usr/local/sbin
>     PERL_BADLANG (unset)
>     SHELL=/pkg/bin/bash

This is gone from all recent Perls, so I'm marking this as resolved.


---
via perlbug:  queue: perl5 status: new
https://rt.perl.org:443/rt3/Ticket/Display.html?id=41344

• [perl #41344] setuid perl: "Setuid script changed" error when root cannot access directory by Brian Fraser via RT