diff options
authorAndrei Vagin <>2019-02-01 14:20:24 -0800
committerLinus Torvalds <>2019-02-01 15:46:23 -0800
commit8fb335e078378c8426fabeed1ebee1fbf915690c (patch)
parenta8e911d13540487942d53137c156bd7707f66e5d (diff)
kernel/exit.c: release ptraced tasks before zap_pid_ns_processes
Currently, exit_ptrace() adds all ptraced tasks in a dead list, then zap_pid_ns_processes() waits on all tasks in a current pidns, and only then are tasks from the dead list released. zap_pid_ns_processes() can get stuck on waiting tasks from the dead list. In this case, we will have one unkillable process with one or more dead children. Thanks to Oleg for the advice to release tasks in find_child_reaper(). Link: Fixes: 7c8bd2322c7f ("exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()") Signed-off-by: Andrei Vagin <> Signed-off-by: Oleg Nesterov <> Cc: "Eric W. Biederman" <> Cc: <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 3fb7be001964..2639a30a8aa5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -558,12 +558,14 @@ static struct task_struct *find_alive_thread(struct task_struct *p)
return NULL;
-static struct task_struct *find_child_reaper(struct task_struct *father)
+static struct task_struct *find_child_reaper(struct task_struct *father,
+ struct list_head *dead)
struct pid_namespace *pid_ns = task_active_pid_ns(father);
struct task_struct *reaper = pid_ns->child_reaper;
+ struct task_struct *p, *n;
if (likely(reaper != father))
return reaper;
@@ -579,6 +581,12 @@ static struct task_struct *find_child_reaper(struct task_struct *father)
panic("Attempted to kill init! exitcode=0x%08x\n",
father->signal->group_exit_code ?: father->exit_code);
+ list_for_each_entry_safe(p, n, dead, ptrace_entry) {
+ list_del_init(&p->ptrace_entry);
+ release_task(p);
+ }
@@ -668,7 +676,7 @@ static void forget_original_parent(struct task_struct *father,
exit_ptrace(father, dead);
/* Can drop and reacquire tasklist_lock */
- reaper = find_child_reaper(father);
+ reaper = find_child_reaper(father, dead);
if (list_empty(&father->children))