"Eric W. Biederman" <ebied...@xmission.com> writes:
> Asking wait_task_inactive to verify that tsk->__state == __TASK_TRACED
> was needed to detect the when ptrace_stop would decide not to stop
> after calling "set_special_state(TASK_TRACED)". With the recent
> cleanups ptrace_stop will always stop after calling set_special_state.
>
> Take advatnage of this by no longer asking wait_task_inactive to
> verify the state. If a bug is hit and wait_task_inactive does not
> succeed warn and return -ESRCH.
As Oleg noticed upthread there are more reasons than simply
!current->ptrace for wait_task_inactive to fail. In particular a fatal
signal can be received any time before JOBCTL_DELAY_SIGKILL.
So this change is not safe. I will respin this one.
Eric
> Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
> ---
> kernel/ptrace.c | 14 +++-----------
> 1 file changed, 3 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 16d1a84a2cae..0634da7ac685 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -265,17 +265,9 @@ static int ptrace_check_attach(struct task_struct
> *child, bool ignore_state)
> }
> read_unlock(&tasklist_lock);
>
> - if (!ret && !ignore_state) {
> - if (!wait_task_inactive(child, __TASK_TRACED)) {
> - /*
> - * This can only happen if may_ptrace_stop() fails and
> - * ptrace_stop() changes ->state back to TASK_RUNNING,
> - * so we should not worry about leaking __TASK_TRACED.
> - */
> - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
> - ret = -ESRCH;
> - }
> - }
> + if (!ret && !ignore_state &&
> + WARN_ON_ONCE(!wait_task_inactive(child, 0)))
> + ret = -ESRCH;
>
> return ret;
> }
Eric
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