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7d24e2df52
linux/kernel
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Oleg Nesterov 7d24e2df52 exit: reparent: fix the cross-namespace PR_SET_CHILD_SUBREAPER reparenting 
find_new_reaper() assumes that "has_child_subreaper" logic is safe as
long as we are not the exiting ->child_reaper and this is doubly wrong:

1. In fact it is safe if "pid_ns->child_reaper == father"; there must
   be no children after zap_pid_ns_processes() returns, so it doesn't
   matter what we return in this case and even pid_ns->child_reaper is
   wrong otherwise: we can't reparent to ->child_reaper == current.

   This is not a bug, but this is confusing.

2. It is not safe if we are not pid_ns->child_reaper but from the same
   thread group. We drop tasklist_lock before zap_pid_ns_processes(),
   so another thread can lock it and choose the new reaper from the
   upper namespace if has_child_subreaper == T, and this is obviously
   wrong.

   This is not that bad, zap_pid_ns_processes() won't return until the
   the new reaper reaps all zombies, but this should be fixed anyway.

We could change for_each_thread() loop to use ->exit_state instead of
PF_EXITING which we had to use until 8aac62706a, or we could change
copy_signal() to check CLONE_NEWPID before setting has_child_subreaper,
but lets change this code so that it is clear we can't look outside of
our namespace, otherwise same_thread_group(reaper, child_reaper) check
will look wrong and confusing anyway.

We can simply start from "father" and fix the problem. We can't wrongly
return a thread from the same thread group if ->is_child_subreaper == T,
we know that all threads have PF_EXITING set.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-10 17:41:17 -08:00
..
bpf bpf: split eBPF out of NET 2014-10-27 19:09:59 -04:00
configs x86: Add "make tinyconfig" to configure the tiniest possible kernel 2014-08-08 16:30:24 -07:00
debug kdb: replace strnicmp with strncasecmp 2014-10-14 02:18:25 +02:00
events Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-09 20:55:37 -08:00
gcov gcov: add ARM64 to GCOV_PROFILE_ALL 2014-10-29 16:33:14 -07:00
irq Merge branch 'irq-irqdomain-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 09:01:01 -08:00
locking locking/mutex: Don't assume TASK_RUNNING 2014-10-28 10:55:08 +01:00
power PM / sleep: Fix entering suspend-to-IDLE if no freeze_oops is set 2014-11-08 22:30:05 +01:00
printk printk: drop logbuf_cpu volatile qualifier 2014-12-10 17:41:11 -08:00
rcu Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD 2014-11-13 10:39:04 -08:00
sched sched_show_task: fix unsafe usage of ->real_parent 2014-12-10 17:41:09 -08:00
time Merge branch 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 10:13:28 -08:00
trace tracing: Do not risk busy looping in buffer splice 2014-11-10 16:47:31 -05:00
.gitignore
acct.c acct: eliminate compile warning 2014-10-09 22:26:04 -04:00
async.c kernel/async.c: switch to pr_foo() 2014-10-09 22:26:04 -04:00
audit_tree.c audit: keep inode pinned 2014-11-11 14:20:22 -05:00
audit_watch.c audit: invalid op= values for rules 2014-09-23 16:37:53 -04:00
audit.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-09 21:21:34 -08:00
audit.h audit: reduce scope of audit_log_fcaps 2014-09-23 16:37:51 -04:00
auditfilter.c Merge git://git.infradead.org/users/eparis/audit 2014-10-19 16:25:56 -07:00
auditsc.c Merge git://git.infradead.org/users/eparis/audit 2014-10-19 16:25:56 -07:00
backtracetest.c kernel/backtracetest.c: replace no level printk by pr_info() 2014-06-04 16:54:14 -07:00
bounds.c page-cgroup: get rid of NR_PCG_FLAGS 2014-08-08 15:57:18 -07:00
capability.c CAPABILITIES: remove undefined caps from all processes 2014-07-24 21:53:47 +10:00
cgroup_freezer.c cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes 2014-07-15 11:05:09 -04:00
cgroup.c Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-10 07:26:02 -04:00
compat.c compat: nanosleep: Clarify error handling 2014-09-06 12:58:18 +02:00
configs.c
context_tracking.c sched: stop the unbound recursion in preempt_schedule_context() 2014-10-28 10:46:05 +01:00
cpu_pm.c
cpu.c cpu: Avoid puts_pending overflow 2014-11-03 19:21:01 -08:00
cpuset.c sched/deadline: Ensure that updates to exclusive cpusets don't break AC 2014-10-28 10:48:00 +01:00
crash_dump.c crash_dump: Make is_kdump_kernel() accessible from modules 2014-08-25 15:42:19 -07:00
cred.c
delayacct.c delayacct: Remove braindamaged type conversions 2014-07-23 10:18:06 -07:00
dma.c
elfcore.c
exec_domain.c kernel/exec_domain.c: code clean-up 2014-06-04 16:54:15 -07:00
exit.c exit: reparent: fix the cross-namespace PR_SET_CHILD_SUBREAPER reparenting 2014-12-10 17:41:17 -08:00
extable.c
fork.c signal: Document the RCU protection of ->sighand 2014-10-29 10:07:18 -07:00
freezer.c freezer: remove obsolete comments in __thaw_task() 2014-10-21 23:44:20 +02:00
futex_compat.c
futex.c futex: Fix a race condition between REQUEUE_PI and task death 2014-10-26 16:16:18 +01:00
groups.c
hung_task.c kernel/hung_task.c: convert simple_strtoul to kstrtouint 2014-06-04 16:54:15 -07:00
irq_work.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
jump_label.c
kallsyms.c kernel/kallsyms.c: use __seq_open_private() 2014-10-14 02:18:16 +02:00
kcmp.c kcmp: fix standard comparison bug 2014-09-10 15:42:12 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER 2014-07-16 14:57:13 +02:00
Kconfig.preempt
kexec.c kexec: remove the unused function parameter 2014-10-14 02:18:21 +02:00
kmod.c usermodehelper: kill the kmod_thread_locker logic 2014-12-10 17:41:17 -08:00
kprobes.c kprobes: Skip kretprobe hit in NMI context to avoid deadlock 2014-08-08 10:38:04 +02:00
ksysfs.c
kthread.c kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations") 2014-10-09 22:25:51 -04:00
latencytop.c kernel/latencytop.c: convert seq_printf to seq_puts 2014-06-04 16:54:15 -07:00
Makefile kernel: res_counter: remove the unused API 2014-12-10 17:41:04 -08:00
module_signing.c
module-internal.h
module.c sched, modules: Fix nested sleep in add_unformed_module() 2014-10-28 10:56:30 +01:00
notifier.c
nsproxy.c namespaces: Use task_lock and not rcu to protect nsproxy 2014-07-29 18:08:50 -07:00
padata.c
panic.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
params.c kernel/param: consolidate __{start,stop}___param[] in <linux/moduleparam.h> 2014-10-14 02:18:28 +02:00
pid_namespace.c
pid.c
profile.c kernel/profile.c: use static const char instead of static char 2014-06-06 16:08:13 -07:00
ptrace.c exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent() 2014-12-10 17:41:10 -08:00
range.c
reboot.c kernel: add support for kernel restart handler call chain 2014-09-26 00:00:06 -07:00
relay.c
resource.c x86: optimize resource lookups for ioremap 2014-10-14 02:18:22 +02:00
seccomp.c Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-14 02:27:06 +02:00
signal.c Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 09:34:43 -08:00
smp.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
smpboot.c sched, smp: Correctly deal with nested sleeps 2014-10-28 10:56:24 +01:00
smpboot.h
softirq.c rcu: Remove "cpu" argument to rcu_note_context_switch() 2014-11-03 19:20:34 -08:00
stacktrace.c
stop_machine.c kernel/stop_machine.c: kernel-doc warning fix 2014-06-04 16:54:15 -07:00
sys_ni.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-10-08 21:40:54 -04:00
sys.c x86, mpx: On-demand kernel allocation of bounds tables 2014-11-18 00:58:53 +01:00
sysctl_binary.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
sysctl.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
system_certificates.S
system_keyring.c KEYS: validate certificate trust only with builtin keys 2014-07-17 09:35:17 -04:00
task_work.c
taskstats.c scheduler: Replace __get_cpu_var with this_cpu_ptr 2014-08-26 13:45:45 -04:00
test_kprobes.c kernel/test_kprobes.c: use current logging functions 2014-08-08 15:57:18 -07:00
torture.c torture: Address race in module cleanup 2014-09-16 13:41:06 -07:00
tracepoint.c tracing: syscall_regfunc() should not skip kernel threads 2014-06-21 00:15:26 -04:00
tsacct.c sched: Make task->start_time nanoseconds based 2014-07-23 10:18:05 -07:00
uid16.c
up.c
user_namespace.c proc: constify seq_operations 2014-08-08 15:57:22 -07:00
user-return-notifier.c scheduler: Replace __get_cpu_var with this_cpu_ptr 2014-08-26 13:45:45 -04:00
user.c kernel/user.c: drop unused field 'files' from user_struct 2014-06-04 16:54:16 -07:00
utsname_sysctl.c sysctl: convert use of typedef ctl_table to struct ctl_table 2014-06-06 16:08:16 -07:00
utsname.c namespaces: Use task_lock and not rcu to protect nsproxy 2014-07-29 18:08:50 -07:00
watchdog.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
workqueue_internal.h
workqueue.c workqueue: Use cond_resched_rcu_qs macro 2014-10-06 05:58:26 -07:00