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Message-ID: <CAGXu5j+C-LQT2z+J3jEJYmftt1jOnMujNjKqgy0JFwM7b_FPjQ@mail.gmail.com> Date: Mon, 21 Nov 2011 10:40:25 -0800 From: Kees Cook <keescook@...omium.org> To: Solar Designer <solar@...nwall.com> Cc: kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org Subject: Re: [PATCH 3/3] security: Yama: add ptrace relationship tracking interface On Sat, Nov 19, 2011 at 8:59 AM, Solar Designer <solar@...nwall.com> wrote: > On Sat, Nov 19, 2011 at 08:30:58PM +0400, Vasiliy Kulikov wrote: >> On Wed, Oct 26, 2011 at 16:49 -0700, Kees Cook wrote: >> > + if (mode == PTRACE_MODE_ATTACH && >> > + ptrace_scope && >> > + !capable(CAP_SYS_PTRACE) && >> > + !task_is_descendant(current, child) && >> > + !ptracer_exception_found(current, child)) >> > + rc = -EPERM; >> >> capable() is better to put after all other tests > > Right, but... > >> as a failed capable() >> might emit a false positive warning into logs or something. > > ...primarily for another reason: a successful capable() sets > PF_SUPERPRIV, whereas the permission might have been granted without > capable() as well. The PF_SUPERPRIV flag is visible via BSD process > accounting. Fair point, I'll move it. I had to go look up an earlier thread since this was ringing a bell, but in there I was talking about moving it to the end of the tests too. :) https://lkml.org/lkml/2010/6/30/5 -Kees -- Kees Cook ChromeOS Security
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