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Date: Thu, 6 Oct 2022 21:50:28 +0300 From: Mike Rapoport <rppt@...nel.org> To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com> Cc: "keescook@...omium.org" <keescook@...omium.org>, "bsingharora@...il.com" <bsingharora@...il.com>, "hpa@...or.com" <hpa@...or.com>, "Syromiatnikov, Eugene" <esyr@...hat.com>, "peterz@...radead.org" <peterz@...radead.org>, "rdunlap@...radead.org" <rdunlap@...radead.org>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>, "Eranian, Stephane" <eranian@...gle.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "fweimer@...hat.com" <fweimer@...hat.com>, "nadav.amit@...il.com" <nadav.amit@...il.com>, "jannh@...gle.com" <jannh@...gle.com>, "dethoma@...rosoft.com" <dethoma@...rosoft.com>, "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>, "kcc@...gle.com" <kcc@...gle.com>, "bp@...en8.de" <bp@...en8.de>, "oleg@...hat.com" <oleg@...hat.com>, "hjl.tools@...il.com" <hjl.tools@...il.com>, "Yang, Weijiang" <weijiang.yang@...el.com>, "Lutomirski, Andy" <luto@...nel.org>, "pavel@....cz" <pavel@....cz>, "arnd@...db.de" <arnd@...db.de>, "Moreira, Joao" <joao.moreira@...el.com>, "tglx@...utronix.de" <tglx@...utronix.de>, "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>, "x86@...nel.org" <x86@...nel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>, "john.allen@....com" <john.allen@....com>, "mingo@...hat.com" <mingo@...hat.com>, "Shankar, Ravi V" <ravi.v.shankar@...el.com>, "corbet@....net" <corbet@....net>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>, "gorcunov@...il.com" <gorcunov@...il.com> Subject: Re: [PATCH v2 23/39] x86: Introduce userspace API for CET enabling On Mon, Oct 03, 2022 at 10:51:02PM +0000, Edgecombe, Rick P wrote: > CC Mike about ptrace/CRIU question. > > On Mon, 2022-10-03 at 12:01 -0700, Kees Cook wrote: > > On Thu, Sep 29, 2022 at 03:29:20PM -0700, Rick Edgecombe wrote: > > > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> > > > > > > Add three new arch_prctl() handles: > > > > > > - ARCH_CET_ENABLE/DISABLE enables or disables the specified > > > feature. Returns 0 on success or an error. > > > > > > - ARCH_CET_LOCK prevents future disabling or enabling of the > > > specified feature. Returns 0 on success or an error > > > > > > The features are handled per-thread and inherited over > > > fork(2)/clone(2), > > > but reset on exec(). ... > > > +#include <linux/sched.h> > > > +#include <linux/bitops.h> > > > +#include <asm/prctl.h> > > > + > > > +long cet_prctl(struct task_struct *task, int option, unsigned long > > > features) > > > +{ > > > + if (option == ARCH_CET_LOCK) { > > > + task->thread.features_locked |= features; > > > + return 0; > > > + } > > > + > > > + /* Don't allow via ptrace */ > > > + if (task != current) > > > + return -EINVAL; > > > > ... but locking _is_ allowed via ptrace? If that intended, it should > > be > > explicitly mentioned in the commit log and in a comment here. > > I believe CRIU needs to lock via ptrace as well. Maybe Mike can > confirm. Actually, I didn't use ptrace for locking, I did it with "plain" arch_prctl(). I still can't say for sure CRIU won't need this, I didn't have time yet to have a closer look at this set. -- Sincerely yours, Mike.
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