Messages in this thread | | | Date | Tue, 9 Jan 2018 15:17:13 +0100 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET_NOPTI to enable/disable PTI |
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On Tue, Jan 09, 2018 at 01:56:16PM +0100, Willy Tarreau wrote: > This allows to report the current state of the PTI protection and to > enable or disable it for the current process. The state change is only > allowed if the mm is not shared (no threads have been created yet). > > Setting the flag to disable the protection is subject to CAP_SYS_RAWIO. > However it is possible to re-enable the protection without this privilege. > > Signed-off-by: Willy Tarreau <w@1wt.eu> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Brian Gerst <brgerst@gmail.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Kees Cook <keescook@chromium.org> > > v2: > - use {set,clear}_thread_flag() as recommended by Peter > - use task->mm->context.pti_disable instead of task flag > - check for mm_users == 1 > - check for CAP_SYS_RAWIO only when setting, not clearing > - make the code depend on CONFIG_PAGE_TABLE_ISOLATION > --- > arch/x86/include/uapi/asm/prctl.h | 3 +++ > arch/x86/kernel/process_64.c | 15 +++++++++++++++ > 2 files changed, 18 insertions(+) > > diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h > index 5a6aac9..1f1b5bc 100644 > --- a/arch/x86/include/uapi/asm/prctl.h > +++ b/arch/x86/include/uapi/asm/prctl.h > @@ -10,6 +10,9 @@ > #define ARCH_GET_CPUID 0x1011 > #define ARCH_SET_CPUID 0x1012 > > +#define ARCH_GET_NOPTI 0x1021 > +#define ARCH_SET_NOPTI 0x1022 > + > #define ARCH_MAP_VDSO_X32 0x2001 > #define ARCH_MAP_VDSO_32 0x2002 > #define ARCH_MAP_VDSO_64 0x2003 > diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c > index c754662..9516310 100644 > --- a/arch/x86/kernel/process_64.c > +++ b/arch/x86/kernel/process_64.c > @@ -654,7 +654,22 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) > ret = put_user(base, (unsigned long __user *)arg2); > break; > } > +#ifdef CONFIG_PAGE_TABLE_ISOLATION
Actually, I meant to add a new CONFIG item only for this feature which depends on CONFIG_PAGE_TABLE_ISOLATION. So that people can disable the per-mm thing when they don't want it.
Thx.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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