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SubjectRe: [PATCH 9/9] ptrace: Don't change __state
On 04/26, Eric W. Biederman wrote:
>
> @@ -253,7 +252,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
> */
> if (lock_task_sighand(child, &flags)) {
> if (child->ptrace && child->parent == current) {
> - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
> + WARN_ON(child->jobctl & JOBCTL_DELAY_WAKEKILL);

This WARN_ON() doesn't look right.

It is possible that this child was traced by another task and PTRACE_DETACH'ed,
but it didn't clear DELAY_WAKEKILL.

If the new debugger attaches and calls ptrace() before the child takes siglock
ptrace_freeze_traced() will fail, but we can hit this WARN_ON().

Oleg.

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