Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang afterPTRACE_ATTACH

[Roland McGrath]

> Actually I was thinking along this line.  We can allow
> PTRACE_GETSIGINFO to proceed without forcing the tracee into TRACED
> state, the rationale being the operation is required to tell between
> group stop and ptrace trap.  Am I missing something?

The reason for the transition to TASK_TRACED is to prevent a race with
SIGCONT waking the task.  There is always a race with SIGKILL waking it,
but the circumstances where that can really matter are far fewer.
You need to make sure that the work PTRACE_GETSIGINFO does to access
last_siginfo cannot race with that pointer disappearing or the stack
space it points to becoming invalid.  I think the use of siglock ensures
that, but Oleg should verify it.


Thanks,
Roland
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