From: Oleg Nesterov <oleg@tv-sign.ru>
To: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Roland McGrath <roland@redhat.com>,
Scott James Remnant <scott@ubuntu.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
Date: Fri, 23 Nov 2007 13:54:57 +0300 [thread overview]
Message-ID: <20071123105457.GA93@tv-sign.ru> (raw)
In-Reply-To: <20071123102351.GD6240@localhost.sw.ru>
On 11/23, Alexey Dobriyan wrote:
>
> On Thu, Nov 22, 2007 at 07:14:59PM +0300, Oleg Nesterov wrote:
> > If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist
> > and then changes the ->state from TASK_TRACED to TASK_RUNNING.
> >
> > This can fool another tracer which attaches to us in between. Change the ->state
> > under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed.
>
> ptrace_check_attach? Both do read_lock -- can run in parallel,
Yep.
> so how can it help?
read_lock prevents ptrace_attach(), so the new tracer can't attach
and then do ptrace_check_attach().
Oleg.
next prev parent reply other threads:[~2007-11-23 10:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-22 16:14 [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach Oleg Nesterov
2007-11-23 10:23 ` Alexey Dobriyan
2007-11-23 10:54 ` Oleg Nesterov [this message]
2007-12-11 1:36 ` Roland McGrath
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