Messages in this thread | | | Date | Fri, 9 Jun 2017 18:10:31 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v7 24/26] x86: Enable User-Mode Instruction Prevention |
| |
On Fri, May 05, 2017 at 11:17:22AM -0700, Ricardo Neri wrote: > User_mode Instruction Prevention (UMIP) is enabled by setting/clearing a > bit in %cr4. > > It makes sense to enable UMIP at some point while booting, before user > spaces come up. Like SMAP and SMEP, is not critical to have it enabled > very early during boot. This is because UMIP is relevant only when there is > a userspace to be protected from. Given the similarities in relevance, it > makes sense to enable UMIP along with SMAP and SMEP. > > UMIP is enabled by default. It can be disabled by adding clearcpuid=514 > to the kernel parameters. > > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: H. Peter Anvin <hpa@zytor.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Brian Gerst <brgerst@gmail.com> > Cc: Chen Yucong <slaoub@gmail.com> > Cc: Chris Metcalf <cmetcalf@mellanox.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Fenghua Yu <fenghua.yu@intel.com> > Cc: Huang Rui <ray.huang@amd.com> > Cc: Jiri Slaby <jslaby@suse.cz> > Cc: Jonathan Corbet <corbet@lwn.net> > Cc: Michael S. Tsirkin <mst@redhat.com> > Cc: Paul Gortmaker <paul.gortmaker@windriver.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> > Cc: Shuah Khan <shuah@kernel.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Tony Luck <tony.luck@intel.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Liang Z. Li <liang.z.li@intel.com> > Cc: Alexandre Julliard <julliard@winehq.org> > Cc: Stas Sergeev <stsp@list.ru> > Cc: x86@kernel.org > Cc: linux-msdos@vger.kernel.org > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> > --- > arch/x86/Kconfig | 10 ++++++++++ > arch/x86/kernel/cpu/common.c | 16 +++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 702002b..1b1bbeb 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1745,6 +1745,16 @@ config X86_SMAP > > If unsure, say Y. > > +config X86_INTEL_UMIP > + def_bool y
That's a bit too much. It makes sense on distro kernels but how many machines out there actually have UMIP?
> + depends on CPU_SUP_INTEL > + prompt "Intel User Mode Instruction Prevention" if EXPERT > + ---help--- > + The User Mode Instruction Prevention (UMIP) is a security > + feature in newer Intel processors. If enabled, a general > + protection fault is issued if the instructions SGDT, SLDT, > + SIDT, SMSW and STR are executed in user mode. > + > config X86_INTEL_MPX > prompt "Intel MPX (Memory Protection Extensions)" > def_bool n > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 8ee3211..66ebded 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -311,6 +311,19 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c) > } > } > > +static __always_inline void setup_umip(struct cpuinfo_x86 *c) > +{ > + if (cpu_feature_enabled(X86_FEATURE_UMIP) && > + cpu_has(c, X86_FEATURE_UMIP))
Hmm, so if UMIP is not build-time disabled, the cpu_feature_enabled() will call static_cpu_has().
Looks like you want to call cpu_has() too because alternatives haven't run yet and static_cpu_has() will reply wrong. Please state that in a comment.
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
| |