diff options
| author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-09-02 14:35:48 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-09-02 19:21:38 -0700 |
| commit | add0d4dfd660e9e4fd0af3eac3cad23583c9558f (patch) | |
| tree | 8bba7c39efcd5999c0925bed083a0ca68d6a5e40 /kernel | |
| parent | e385ea63f44b475e034a78b6d8bc6bb50caf72ca (diff) | |
| download | linux-add0d4dfd660e9e4fd0af3eac3cad23583c9558f.tar.bz2 | |
pid_ns: zap_pid_ns_processes: fix the ->child_reaper changing
zap_pid_ns_processes() sets pid_ns->child_reaper = NULL, this is wrong.
Yes, we have already killed all tasks in this namespace, and sys_wait4()
doesn't see any child. But this doesn't mean ->children list is empty, we
may have EXIT_DEAD tasks which are not visible to do_wait(). In that case
the subsequent forget_original_parent() will crash the kernel because it
will try to re-parent these tasks to the NULL reaper.
Even if there are no childs, it is not good that forget_original_parent()
uses reaper == NULL.
Change the code to set ->child_reaper = init_pid_ns.child_reaper instead.
We could use pid_ns->parent->child_reaper as well, I think this does not
really matter. These EXIT_DEAD tasks are not visible to the new ->parent
after re-parenting, they will silently do release_task() eventually.
Note that we must change ->child_reaper, otherwise
forget_original_parent() will use reaper == father, and in that case we
will hit the (correct) BUG_ON(!list_empty(&father->children)).
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/pid_namespace.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index ea567b78d1aa..598f1eec9826 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -179,9 +179,12 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns) rc = sys_wait4(-1, NULL, __WALL, NULL); } while (rc != -ECHILD); - - /* Child reaper for the pid namespace is going away */ - pid_ns->child_reaper = NULL; + /* + * We can not clear ->child_reaper or leave it alone. + * There may by stealth EXIT_DEAD tasks on ->children, + * forget_original_parent() must move them somewhere. + */ + pid_ns->child_reaper = init_pid_ns.child_reaper; acct_exit_ns(pid_ns); return; } |