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Date: Sun, 20 Jan 2013 20:35:42 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
        Kernel Security <security@kernel.org>,
        Michael Davidson <md@google.com>,
        Suleiman Souhlal <suleiman@google.com>, Julien Tinnes <jln@google.com>,
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        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
        Roland McGrath <roland@hack.frob.com>, Tony Luck <tony.luck@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH 0/4] (Was: ptrace: prevent PTRACE_SETREGS from
	corrupting stack)
Message-ID: <20130120193542.GA9241@redhat.com>
References: <20130116181830.GA6469@redhat.com> <CA+55aFzkWqSEzw9oa5JodrM2NWE0H_AF7xyzRhd+DQ=PB=ZT2A@mail.gmail.com> <20130118153700.GA27915@redhat.com> <CA+55aFxEow_-PoX0xFa07yOi6az=6uVx8zeOsfToErmzh7dB8A@mail.gmail.com> <20130118172854.GA29753@redhat.com> <20130118175224.GA520@redhat.com> <CA+55aFyEsU-pkX557A-m+xoGkA_v+fXEyA8z8HbJ5J8K1jObeg@mail.gmail.com> <20130118185559.GA3773@redhat.com> <CA+55aFy=newnMbx53HipyWbRs2mUUPSqXXCpSfDLW78gkro37g@mail.gmail.com> <20130120192448.GA6771@redhat.com>
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On 01/20, Oleg Nesterov wrote:
>
> > And we'd need to make sure to re-set the WAKEKILL flag not just in all
> > the callers of ptrace_check_attach(), but also in the failure case of
> > wait_task_inactive(). I'm not sure it can actually fail if we cleared
> > WAKEKILL, but it's all pretty subtle.
>
> Afaics it can't fail if we clear WAKEKILL... So 2/4 assumes it should
> always succeed and adds the warning.

Argh! It can, exactly because we can not kill may_ptrace_stop() yet.
I'll update and resend 2/4.

Oleg.