linux-kernel - [PATCH 0/3] resend, ptrace && SIGKILL fixes

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Date:	Mon, 16 Jun 2008 18:20:16 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Matthew Wilcox <matthew@....cx>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] resend, ptrace && SIGKILL fixes

On 06/10, Oleg Nesterov wrote:
>
> These 2 patches don't depend on each other. Each change is user visible,
> and I am not really sure it can't confuse debuggers/etc. The explicit
> ack/nack from maintainers is wanted.

I'm mostly worried about do_exit()->ptrace_notify(), with these patches
we never notify the tracer if the tracee was SIGKILL'ed. The current
behaviour depends on arch_ptrace_stop_needed(), this is not good either.

Anyway, I think these patches are fixes. Suppose we send SIGKILL to the
traced task which does ptrace_notify(). If the signal is delivered before
ptrace_notify() takes ->siglock, the tracee sleeps in TASK_TRACED state
and becomes "unkillable". If ptrace_notify() wins, we kill the tracee.
This can't be good.

The 3rd patch is new.

Oleg.

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