Fix for the "error disabling cgroup" error
Sapan Bhatia [Wed, 9 Oct 2013 02:43:10 +0000 (22:43 -0400)]
lxcsu

diff --git a/lxcsu b/lxcsu
index c1ad9d1..4f4a2f7 100755 (executable)
--- a/lxcsu
+++ b/lxcsu
@@ -12,254 +12,256 @@ drop_capabilities='cap_sys_admin,cap_sys_boot,cap_sys_module'
 debug = False
 
 def getarch(f):
-    output = os.popen('readelf -h %s 2>&1'%f).readlines()
-    classlines = [x for x in output if ('Class' in x.split(':')[0])]
-    line = classlines[0]
-    c = line.split(':')[1]
-    if ('ELF64' in c):
-        return 'x86_64'
-    elif ('ELF32' in c):
-        return 'i686'
-    else:
-        raise Exception('Could not determine architecture')
-
-def umount(fs_dir):
-    output = os.popen('/bin/umount %s 2>&1'%fs_dir).read()
-    return ('device is busy' not in output)
+       output = os.popen('readelf -h %s 2>&1'%f).readlines()
+       classlines = [x for x in output if ('Class' in x.split(':')[0])]
+       line = classlines[0]
+       c = line.split(':')[1]
+       if ('ELF64' in c):
+               return 'x86_64'
+       elif ('ELF32' in c):
+               return 'i686'
+       else:
+               raise Exception('Could not determine architecture')
+
+def umount(fs_dir, opts=''):
+       output = os.popen('/bin/umount %s %s 2>&1'%(opts, fs_dir)).read()
+       return ('device is busy' not in output)
 
 def main ():
-    parser = ArgumentParser()
-    parser.add_argument("-n", "--nonet",
-                        action="store_true", dest="netns", default=False,
-                        help="Don't enter network namespace")
-    parser.add_argument("-m", "--nomnt",
-                        action="store_true", dest="mntns", default=False,
-                        help="Don't enter mount namespace")
-    parser.add_argument("-p", "--nopid",
-                        action="store_true", dest="pidns", default=False,
-                        help="Don't enter pid namespace")
-    parser.add_argument("-r", "--root",
-                        action="store_true", dest="root", default=False,
-                        help="Enter as root: be careful")
-    parser.add_argument("-i","--internal",
-                        action="store_true", dest="internal", default=False,
-                        help="does *not* prepend '-- -c' to arguments - or invoke lxcsu-internal")
-    parser.add_argument("-d","--debug",
-                        action='store_true', dest='debug', default=False,
-                        help="debug option")
-    parser.add_argument("-s","--nosliceuid",
-                        action='store_true', dest="nosliceuid", default=False,
-                        help="do not change to slice uid inside of slice")
-    parser.add_argument("-o","--noslicehome",
-                        action='store_true', dest="noslicehome", default=False,
-                        help="do not change to slice home directory inside of slice")
-
-    if os.path.exists("/etc/lxcsu_default"):
-        defaults = parser.parse_args(file("/etc/lxcsu_default","r").read().split())
-        parser.set_defaults(**defaults.__dict__)
-
-    parser.add_argument ("slice_name")
-    parser.add_argument ("command_to_run",nargs="*")
-
-    args = parser.parse_args()
-    slice_name=args.slice_name
-
-    # unless we run the symlink 'lxcsu-internal', or we specify the -i option, prepend '--' '-c'
-    if sys.argv[0].find('internal')>=0: args.internal=True
-
-    if len(args.command_to_run)>0 and (args.command_to_run[0] == "/sbin/service"):
-        # A quick hack to support nodemanager interfaces.py when restarting
-        # networking in a slice.
-        args.nosliceuid = True
-
-    # plain lxcsu
-    if not args.internal:
-        # no command given: enter interactive shell
-        if not args.command_to_run: args.command_to_run=['/bin/sh']
-        args.command_to_run = [ '-c' ] + [" ".join(args.command_to_run)]
-
-    # support for either setting debug at the top of this file, or on the command-line
-    if args.debug:
-        global debug
-        debug=True
-
-    try:
-        cmd = 'grep %s /proc/*/cgroup | grep freezer'%slice_name
-        output = os.popen(cmd).readlines()
-    except:
-        print "Error finding slice %s"%slice_name
-        exit(1)
-
-    slice_spec = None
-
-    # provide a default as this is not always properly computed
-    arch = None
-
-    for e in output:
-        try:
-            l = e.rstrip()
-            path = l.split(':')[0]  
-            comp = l.rsplit(':')[-1]
-            slice_name_check = comp.rsplit('/')[-1]
-            if debug: print "dealing with >%s<"%slice_name_check
-            
-            if (slice_name_check == slice_name):
-                if debug: print "found %s"%slice_name
-                slice_path = path
-                pid = slice_path.split('/')[2]
-                cmdline = open('/proc/%s/cmdline'%pid).read().rstrip('\n\x00')
-                if (cmdline == '/sbin/init') or (cmdline.startswith("init [")):
-                    slice_spec = slice_path
-                    arch = getarch('/proc/%s/exe'%pid)
-                    break
-        except Exception,e:
-            if debug: 
-                import traceback
-                print "BEG lxcsu - ignoring exception"
-                traceback.print_exc()
-                print "END lxcsu - ignoring exception"
-            pass
-
-    if (not slice_spec or not pid):
-        print "Not started: %s"%slice_name
-        exit(1)
-
-    if arch is None:
-        arch = 'x86_64'
-
-    # Set sysctls specific to slice
-    sysctls = []
-    sysctl_dir = '/etc/planetlab/vsys-attributes/%s'%slice_name
-    if (os.access(sysctl_dir,0)):
-        entries = os.listdir(sysctl_dir)
-        for e in entries:
-            prefix = 'vsys_sysctl.'
-            if (e.startswith(prefix)):
-                sysctl_file = '/'.join([sysctl_dir,e])
-                sysctl_name = e[len(prefix):]
-                sysctl_val = open(sysctl_file).read()
-                sysctls.append((sysctl_file, sysctl_name, sysctl_val))
-
-    # Enter cgroups
-    try:
-        for subsystem in ['cpuset','memory','blkio']:
-            open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))
-
-    except:
-        print "Error assigning resources: %s"%slice_name
-        exit(1)
-
-    try:
-        open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))
-    except:
-        print "Error assigning cpuacct: %s" % slice_name
-        exit(1)
-
-    # If the slice is frozen, then we'll get an EBUSY when trying to write to the task
-    # list for the freezer cgroup. Since the user couldn't do anything anyway, it's best
-    # in this case to error out the shell. (an alternative would be to un-freeze it,
-    # add the task, and re-freeze it)
-    try:
-        f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')
-        f.write(str(os.getpid()))
-        # note: we need to call f.close() explicitly, or we'll get an exception in
-        # the object destructor, which will not be caught
-        f.close()
-    except:
-        print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name
-        exit(1)
-
-    setns.chcontext('/proc/%s/ns/uts'%pid)
-    setns.chcontext('/proc/%s/ns/ipc'%pid)
-    
-    if (not args.pidns):
-        setns.chcontext('/proc/%s/ns/pid'%pid)
-
-    if (not args.netns):
-        setns.chcontext('/proc/%s/ns/net'%pid)
-
-    if (not args.mntns):
-        setns.chcontext('/proc/%s/ns/mnt'%pid)
-
-    proc_mounted = False
-    if (not os.access('/proc/self',0)):
-        proc_mounted = True
-        setns.proc_mount()
-
-    for (sysctl_file, sysctl_name, sysctl_val) in sysctls:
-                for fn in ["/sbin/sysctl", "/usr/sbin/sysctl", "/bin/sysctl", "/usr/bin/sysctl"]:
-                    if os.path.exists(fn):
-                        os.system('%s -w %s=%s'%(fn, sysctl_name,sysctl_val))
-                        break
-                else:
-                    print "Error: image does not have a sysctl binary"
-
-    # cgroups is not yet LXC-safe, so we need to use the coarse grained access control
-    # strategy of unmounting the filesystem
-
-    umount_result = True
-    for subsystem in ['cpuset','cpu,cpuacct','memory','devices','freezer','net_cls','blkio','perf_event']:
-        fs_path = '/sys/fs/cgroup/%s'%subsystem
-        if (not umount(fs_path)):
-            print "Error disabling cgroup access"
-            exit(1)
-
-    if (not umount('/sys/fs/cgroup')):
-        print "Error disabling cgroup access"
-        exit(1)
-
-    pid = os.fork()
-
-    # capsh has a --user option starting with f14
-    # so if only for f12 we need to fake this one
-    #
-    # capsh.c does essentially the following when invoked with --user:
-    #      pwd = getpwnam(user); ...
-    #      ngroups = MAX_GROUPS; 
-    #      status = getgrouplist(user, pwd->pw_gid, groups, &ngroups); ...
-    #      status = setgroups(ngroups, groups); ...
-    #      status = setgid(pwd->pw_gid); ...
-    #      status = setuid(pwd->pw_uid); ...
-    # however we cannot simulate that ourselves because if we did in this process then
-    # capsh could not be allowed to mess with caps any more
-
-    def getuid (slicename):
-        import pwd
-        try:
-            return pwd.getpwnam(slicename).pw_uid
-        except:
-            return
-
-    if (pid == 0):
-        cap_arg = '--drop='+drop_capabilities
-
-        if (not args.root):
-            if (args.nosliceuid):
-                # we still want to drop capabilities, but don't want to switch UIDs
-                exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--','--login',]+args.command_to_run
-            else:
-                uid = getuid (slice_name)
-                if not uid:
-                    print "lxcsu could not spot %s in /etc/passwd - exiting"%slice_name
-                    exit(1)
-                exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--uid=%s'%uid,'--','--login',]+args.command_to_run
+       parser = ArgumentParser()
+       parser.add_argument("-n", "--nonet",
+                                               action="store_true", dest="netns", default=False,
+                                               help="Don't enter network namespace")
+       parser.add_argument("-m", "--nomnt",
+                                               action="store_true", dest="mntns", default=False,
+                                               help="Don't enter mount namespace")
+       parser.add_argument("-p", "--nopid",
+                                               action="store_true", dest="pidns", default=False,
+                                               help="Don't enter pid namespace")
+       parser.add_argument("-r", "--root",
+                                               action="store_true", dest="root", default=False,
+                                               help="Enter as root: be careful")
+       parser.add_argument("-i","--internal",
+                                               action="store_true", dest="internal", default=False,
+                                               help="does *not* prepend '-- -c' to arguments - or invoke lxcsu-internal")
+       parser.add_argument("-d","--debug",
+                                               action='store_true', dest='debug', default=False,
+                                               help="debug option")
+       parser.add_argument("-s","--nosliceuid",
+                                               action='store_true', dest="nosliceuid", default=False,
+                                               help="do not change to slice uid inside of slice")
+       parser.add_argument("-o","--noslicehome",
+                                               action='store_true', dest="noslicehome", default=False,
+                                               help="do not change to slice home directory inside of slice")
+
+       if os.path.exists("/etc/lxcsu_default"):
+               defaults = parser.parse_args(file("/etc/lxcsu_default","r").read().split())
+               parser.set_defaults(**defaults.__dict__)
+
+       parser.add_argument ("slice_name")
+       parser.add_argument ("command_to_run",nargs="*")
+
+       args = parser.parse_args()
+       slice_name=args.slice_name
+
+       # unless we run the symlink 'lxcsu-internal', or we specify the -i option, prepend '--' '-c'
+       if sys.argv[0].find('internal')>=0: args.internal=True
+
+       if len(args.command_to_run)>0 and (args.command_to_run[0] == "/sbin/service"):
+               # A quick hack to support nodemanager interfaces.py when restarting
+               # networking in a slice.
+               args.nosliceuid = True
+
+       # plain lxcsu
+       if not args.internal:
+               # no command given: enter interactive shell
+               if not args.command_to_run: args.command_to_run=['/bin/sh']
+               args.command_to_run = [ '-c' ] + [" ".join(args.command_to_run)]
+
+       # support for either setting debug at the top of this file, or on the command-line
+       if args.debug:
+               global debug
+               debug=True
+
+       try:
+               cmd = 'grep %s /proc/*/cgroup | grep freezer'%slice_name
+               output = os.popen(cmd).readlines()
+       except:
+               print "Error finding slice %s"%slice_name
+               exit(1)
+
+       slice_spec = None
+
+       # provide a default as this is not always properly computed
+       arch = None
+
+       for e in output:
+               try:
+                       l = e.rstrip()
+                       path = l.split(':')[0]  
+                       comp = l.rsplit(':')[-1]
+                       slice_name_check = comp.rsplit('/')[-1]
+                       if debug: print "dealing with >%s<"%slice_name_check
+                       
+                       if (slice_name_check == slice_name):
+                               if debug: print "found %s"%slice_name
+                               slice_path = path
+                               pid = slice_path.split('/')[2]
+                               cmdline = open('/proc/%s/cmdline'%pid).read().rstrip('\n\x00')
+                               if (cmdline == '/sbin/init') or (cmdline.startswith("init [")):
+                                       slice_spec = slice_path
+                                       arch = getarch('/proc/%s/exe'%pid)
+                                       break
+               except Exception,e:
+                       if debug: 
+                               import traceback
+                               print "BEG lxcsu - ignoring exception"
+                               traceback.print_exc()
+                               print "END lxcsu - ignoring exception"
+                       pass
+
+       if (not slice_spec or not pid):
+               print "Not started: %s"%slice_name
+               exit(1)
+
+       if arch is None:
+               arch = 'x86_64'
+
+       # Set sysctls specific to slice
+       sysctls = []
+       sysctl_dir = '/etc/planetlab/vsys-attributes/%s'%slice_name
+       if (os.access(sysctl_dir,0)):
+               entries = os.listdir(sysctl_dir)
+               for e in entries:
+                       prefix = 'vsys_sysctl.'
+                       if (e.startswith(prefix)):
+                               sysctl_file = '/'.join([sysctl_dir,e])
+                               sysctl_name = e[len(prefix):]
+                               sysctl_val = open(sysctl_file).read()
+                               sysctls.append((sysctl_file, sysctl_name, sysctl_val))
+
+       # Enter cgroups
+       try:
+               for subsystem in ['cpuset','memory','blkio']:
+                       open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))
+
+       except:
+               print "Error assigning resources: %s"%slice_name
+               exit(1)
+
+       try:
+               open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))
+       except:
+               print "Error assigning cpuacct: %s" % slice_name
+               exit(1)
+
+       # If the slice is frozen, then we'll get an EBUSY when trying to write to the task
+       # list for the freezer cgroup. Since the user couldn't do anything anyway, it's best
+       # in this case to error out the shell. (an alternative would be to un-freeze it,
+       # add the task, and re-freeze it)
+       try:
+               f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')
+               f.write(str(os.getpid()))
+               # note: we need to call f.close() explicitly, or we'll get an exception in
+               # the object destructor, which will not be caught
+               f.close()
+       except:
+               print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name
+               exit(1)
+
+       setns.chcontext('/proc/%s/ns/uts'%pid)
+       setns.chcontext('/proc/%s/ns/ipc'%pid)
+       
+       if (not args.pidns):
+               setns.chcontext('/proc/%s/ns/pid'%pid)
+
+       if (not args.netns):
+               setns.chcontext('/proc/%s/ns/net'%pid)
+
+       if (not args.mntns):
+               setns.chcontext('/proc/%s/ns/mnt'%pid)
+
+       proc_mounted = False
+       if (not os.access('/proc/self',0)):
+               proc_mounted = True
+               setns.proc_mount()
+
+       for (sysctl_file, sysctl_name, sysctl_val) in sysctls:
+                               for fn in ["/sbin/sysctl", "/usr/sbin/sysctl", "/bin/sysctl", "/usr/bin/sysctl"]:
+                                       if os.path.exists(fn):
+                                               os.system('%s -w %s=%s'%(fn, sysctl_name,sysctl_val))
+                                               break
+                               else:
+                                       print "Error: image does not have a sysctl binary"
+
+       # cgroups is not yet LXC-safe, so we need to use the coarse grained access control
+       # strategy of unmounting the filesystem
+
+       umount_result = True
+       for subsystem in ['cpuset','cpu,cpuacct','memory','devices','freezer','net_cls','blkio','perf_event','systemd']:
+               fs_path = '/sys/fs/cgroup/%s'%subsystem
+               if (not umount(fs_path,'-l')):
+                       pass
+                       # Leaving these comments for historical reference
+                       #print "Error disabling cgroup access"
+                       #exit(1) - Don't need this because failure here implies failure in the call to umount /sys/fs/cgroup
+
+       if (not umount('/sys/fs/cgroup')):
+               print "Error disabling cgroup access"
+               exit(1)
+
+       pid = os.fork()
+
+       # capsh has a --user option starting with f14
+       # so if only for f12 we need to fake this one
+       #
+       # capsh.c does essentially the following when invoked with --user:
+       #               pwd = getpwnam(user); ...
+       #               ngroups = MAX_GROUPS; 
+       #               status = getgrouplist(user, pwd->pw_gid, groups, &ngroups); ...
+       #               status = setgroups(ngroups, groups); ...
+       #               status = setgid(pwd->pw_gid); ...
+       #               status = setuid(pwd->pw_uid); ...
+       # however we cannot simulate that ourselves because if we did in this process then
+       # capsh could not be allowed to mess with caps any more
+
+       def getuid (slicename):
+               import pwd
+               try:
+                       return pwd.getpwnam(slicename).pw_uid
+               except:
+                       return
+
+       if (pid == 0):
+               cap_arg = '--drop='+drop_capabilities
+
+               if (not args.root):
+                       if (args.nosliceuid):
+                               # we still want to drop capabilities, but don't want to switch UIDs
+                               exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--','--login',]+args.command_to_run
+                       else:
+                               uid = getuid (slice_name)
+                               if not uid:
+                                       print "lxcsu could not spot %s in /etc/passwd - exiting"%slice_name
+                                       exit(1)
+                               exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--uid=%s'%uid,'--','--login',]+args.command_to_run
 # once we can drop f12, it would be nicer to instead go for
-#                exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--user=%s'%slice_name,'--','--login',]+args.command_to_run
-        else:
-            exec_args = [arch,'/usr/sbin/capsh','--','--login']+args.command_to_run
-
-        os.environ['SHELL'] = '/bin/sh'
-        if os.path.exists('/etc/planetlab/lib/bind_public.so'):
-            os.environ['LD_PRELOAD'] = '/etc/planetlab/lib/bind_public.so'
-        if not args.noslicehome:
-            os.environ['HOME'] = '/home/%s'%slice_name
-            os.chdir("/home/%s"%(slice_name))
-        if debug: print 'lxcsu:execv:','/usr/bin/setarch',exec_args
-        os.execv('/usr/bin/setarch',exec_args)
-    else:
-        setns.proc_umount()
-        _,status = os.waitpid(pid,0)
-        exit(os.WEXITSTATUS(status))
+#                               exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--user=%s'%slice_name,'--','--login',]+args.command_to_run
+               else:
+                       exec_args = [arch,'/usr/sbin/capsh','--','--login']+args.command_to_run
+
+               os.environ['SHELL'] = '/bin/sh'
+               if os.path.exists('/etc/planetlab/lib/bind_public.so'):
+                       os.environ['LD_PRELOAD'] = '/etc/planetlab/lib/bind_public.so'
+               if not args.noslicehome:
+                       os.environ['HOME'] = '/home/%s'%slice_name
+                       os.chdir("/home/%s"%(slice_name))
+               if debug: print 'lxcsu:execv:','/usr/bin/setarch',exec_args
+               os.execv('/usr/bin/setarch',exec_args)
+       else:
+               setns.proc_umount()
+               _,status = os.waitpid(pid,0)
+               exit(os.WEXITSTATUS(status))
 
 if __name__ == '__main__':
-    main()
+       main()