Commit 64a4096c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

ptrace: ptrace_detach() can no longer race with SIGKILL

ptrace_detach() re-checks ->ptrace under tasklist lock and calls
release_task() if __ptrace_detach() returns true.  This was needed because
the __TASK_TRACED tracee could be killed/untraced, and it could even pass
exit_notify() before we take tasklist_lock.

But this is no longer possible after 9899d11f "ptrace: ensure
arch_ptrace/ptrace_request can never race with SIGKILL".  We can turn
these checks into WARN_ON() and remove release_task().

While at it, document the setting of child->exit_code.
Signed-off-by: default avatarOleg Nesterov <>
Cc: Pavel Labath <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent b72c1869
......@@ -456,8 +456,6 @@ static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
static int ptrace_detach(struct task_struct *child, unsigned int data)
bool dead = false;
if (!valid_signal(data))
return -EIO;
......@@ -467,18 +465,19 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
* This child can be already killed. Make sure de_thread() or
* our sub-thread doing do_wait() didn't do release_task() yet.
* We rely on ptrace_freeze_traced(). It can't be killed and
* untraced by another thread, it can't be a zombie.
if (child->ptrace) {
child->exit_code = data;
dead = __ptrace_detach(current, child);
WARN_ON(!child->ptrace || child->exit_state);
* tasklist_lock avoids the race with wait_task_stopped(), see
* the comment in ptrace_resume().
child->exit_code = data;
__ptrace_detach(current, child);
proc_ptrace_connector(child, PTRACE_DETACH);
if (unlikely(dead))
return 0;
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