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Message-ID: <CAObL_7GSNbgceHQpNx3fbiCbV5u-_vJJO5cptwVCK34W7wFH5Q@mail.gmail.com> Date: Thu, 24 May 2012 17:26:54 -0700 From: Andrew Lutomirski <luto@....edu> To: "H. Peter Anvin" <hpa@...or.com> Cc: James Morris <jmorris@...ei.org>, Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org, mcgrathr@...gle.com, indan@....nu, netdev@...isplace.org, linux-security-module@...r.kernel.org, kernel-hardening@...ts.openwall.com, mingo@...hat.com, oleg@...hat.com, peterz@...radead.org, rdunlap@...otime.net, tglx@...utronix.de, serge.hallyn@...onical.com, pmoore@...hat.com, akpm@...ux-foundation.org, corbet@....net, markus@...omium.org, coreyb@...ux.vnet.ibm.com, keescook@...omium.org, viro@...iv.linux.org.uk Subject: Re: [RFC PATCH 0/3] move the secure_computing call On Thu, May 24, 2012 at 4:56 PM, H. Peter Anvin <hpa@...or.com> wrote: > On 05/24/2012 04:43 PM, Andrew Lutomirski wrote: >> >> IMO the behavior should change. Alternatively, a post-ptrace syscall >> should have to pass the *tracer's* seccomp filter, but that seems >> overcomplicated and confusing. >> >> OTOH, allowing ptrace in a seccomp filter is asking for trouble anyway >> -- if you can ptrace something outside the sandbox, you've escaped. >> > > This is my suggestion: if there is demand, make it possible to install a > *second* seccomp filter program which is run on the result of the > ptrace. I.e.: > > Untraced: process -> seccomp1 -> kernel > > Traced: process -> seccomp1 -> ptrace -> seccomp2 -> kernel Just to clarify: are you suggesting that, for now, the traced behavior should be: process -> seccomp -> ptrace -> kernel? If so, I think the man page or something should have a big fat warning that seccomp filters should *never* allow ptrace (even PTRACE_TRACEME) unless they fully understand the issue. In any case, I think that the UML interaction is missing the point. UML will *emulate* the seccomp filter. If it chooses to use host seccomp filters for some business, that's its business. --Andy
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