From 175aed3f8d38b87d3287bb765c794205f2b511de Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 10 Dec 2014 15:55:08 -0800
Subject: [PATCH] exit: reparent: document the ->has_child_subreaper checks
Swap the "init_task" and same_thread_group() checks. This way it is more
simple to document these checks and we can remove the link to the previous
discussion on lkml.
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>
---
kernel/exit.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index a4204aaba8a2a..576949ce5665c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -495,18 +495,16 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
if (father->signal->has_child_subreaper) {
struct task_struct *reaper;
-
/*
- * Find the first ancestor marked as child_subreaper.
- * Note that the code below checks same_thread_group(reaper,
- * pid_ns->child_reaper). This is what we need to DTRT in a
- * PID namespace. However we still need the check above, see
- * http://marc.info/?l=linux-kernel&m=131385460420380
+ * Find the first ->is_child_subreaper ancestor in our pid_ns.
+ * We start from father to ensure we can not look into another
+ * namespace, this is safe because all its threads are dead.
*/
for (reaper = father;
- reaper != &init_task;
+ !same_thread_group(reaper, pid_ns->child_reaper);
reaper = reaper->real_parent) {
- if (same_thread_group(reaper, pid_ns->child_reaper))
+ /* call_usermodehelper() descendants need this check */
+ if (reaper == &init_task)
break;
if (!reaper->signal->is_child_subreaper)
continue;
--
2.30.2