The patch titled
forget_original_parent: do not abuse child->ptrace_entry
has been added to the -mm tree. Its filename is
forget_original_parent-do-not-abuse-child-ptrace_entry.patch
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------------------------------------------------------
Subject: forget_original_parent: do not abuse child->ptrace_entry
From: Oleg Nesterov <oleg@xxxxxxxxxx>
By discussion with Roland.
- Use ->sibling instead of ->ptrace_entry to chain the need to be
release_task'd childs. Nobody else can use ->sibling, this task
is EXIT_DEAD and nobody can find it on its own list.
- rename ptrace_dead to dead_childs.
- Now that we don't have the "parallel" untrace code, change back
reparent_thread() to return void, pass dead_childs as an argument.
Actually, I don't understand why do we notify /sbin/init when we
reparent a zombie, probably it is better to reap it unconditionally.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: "Metzger, Markus T" <markus.t.metzger@xxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 87 ++++++++++++++++++++++--------------------------
1 file changed, 41 insertions(+), 46 deletions(-)
diff -puN kernel/exit.c~forget_original_parent-do-not-abuse-child-ptrace_entry kernel/exit.c
--- a/kernel/exit.c~forget_original_parent-do-not-abuse-child-ptrace_entry
+++ a/kernel/exit.c
@@ -726,46 +726,6 @@ static void exit_mm(struct task_struct *
mmput(mm);
}
-/* Returns nonzero if the child should be released. */
-static int reparent_thread(struct task_struct *p, struct task_struct *father)
-{
- int dead;
-
- if (p->pdeath_signal)
- /* We already hold the tasklist_lock here. */
- group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
-
- list_move_tail(&p->sibling, &p->real_parent->children);
-
- if (task_detached(p))
- return 0;
- /* If this is a threaded reparent there is no need to
- * notify anyone anything has happened.
- */
- if (same_thread_group(p->real_parent, father))
- return 0;
-
- /* We don't want people slaying init. */
- p->exit_signal = SIGCHLD;
-
- /* If we'd notified the old parent about this child's death,
- * also notify the new parent.
- */
- dead = 0;
- if (!p->ptrace &&
- p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
- do_notify_parent(p, p->exit_signal);
- if (task_detached(p)) {
- p->exit_state = EXIT_DEAD;
- dead = 1;
- }
- }
-
- kill_orphaned_pgrp(p, father);
-
- return dead;
-}
-
/*
* When we die, we re-parent all our children.
* Try to give them to another thread in our thread
@@ -805,10 +765,46 @@ static struct task_struct *find_new_reap
return pid_ns->child_reaper;
}
+/*
+* Any that need to be release_task'd are put on the @dead list.
+ */
+static void reparent_thread(struct task_struct *father, struct task_struct *p,
+ struct list_head *dead)
+{
+ if (p->pdeath_signal)
+ group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
+
+ list_move_tail(&p->sibling, &p->real_parent->children);
+
+ if (task_detached(p))
+ return;
+ /*
+ * If this is a threaded reparent there is no need to
+ * notify anyone anything has happened.
+ */
+ if (same_thread_group(p->real_parent, father))
+ return;
+
+ /* We don't want people slaying init. */
+ p->exit_signal = SIGCHLD;
+
+ /* If it has exited notify the new parent about this child's death. */
+ if (!p->ptrace &&
+ p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
+ do_notify_parent(p, p->exit_signal);
+ if (task_detached(p)) {
+ p->exit_state = EXIT_DEAD;
+ list_move_tail(&p->sibling, dead);
+ }
+ }
+
+ kill_orphaned_pgrp(p, father);
+}
+
static void forget_original_parent(struct task_struct *father)
{
struct task_struct *p, *n, *reaper;
- LIST_HEAD(ptrace_dead);
+ LIST_HEAD(dead_childs);
exit_ptrace(father);
@@ -821,15 +817,14 @@ static void forget_original_parent(struc
BUG_ON(p->ptrace);
p->parent = p->real_parent;
}
- if (reparent_thread(p, father))
- list_add(&p->ptrace_entry, &ptrace_dead);;
+ reparent_thread(father, p, &dead_childs);
}
-
write_unlock_irq(&tasklist_lock);
+
BUG_ON(!list_empty(&father->children));
- list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
- list_del_init(&p->ptrace_entry);
+ list_for_each_entry_safe(p, n, &dead_childs, sibling) {
+ list_del_init(&p->sibling);
release_task(p);
}
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
linux-next.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
get_mm_hiwater_xxx-trivial-s-define-inline.patch
getrusage-fill-ru_maxrss-value.patch
ptrace-kill-__ptrace_detach-fix-exit_state-check.patch
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit-fix.patch
ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch
reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch
reparent_thread-fix-the-is-it-traced-check.patch
reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch
forget_original_parent-split-out-the-un-ptrace-part.patch
forget_original_parent-do-not-abuse-child-ptrace_entry.patch
forget_original_parent-do-not-abuse-child-ptrace_entry-fix.patch
move-exit_ptrace-from-forget_original_parent-to-do_exit.patch
reparent-untrace-do-nothing-if-no-childs-tracees.patch
tracehook_notify_death-use-task_detached-helper.patch
workqueue-avoid-recursion-in-run_workqueue.patch
kthreads-move-sched-realeted-initialization-from-kthreadd-context.patch
kthreads-simplify-the-startup-synchronization.patch
kthreads-rework-kthread_stop.patch
kthreads-simplify-migration_thread-exit-path.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch
--
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