[MODERATED] Re: Slow Randomizing Boosts Denial of Service - Bulletin #2

On Tue, Apr 28, 2020 at 05:48:49PM +0200, speck for Thomas Gleixner wrote:
> Folks!
>=20
> I've merged the documentation update from Josh into the master branch of
> the speck git repository at:
>=20
>    cvs.ou.linutronix.de:linux/speck/linux

Ok, since the CRD has been pushed by a ~month, we probably should start
merging the non-critical pieces because we have users for them and
there's no point in letting them rot in an out-of-tree repo.

Of course, we won't change the SHA1's so that no ongoing backports are
disrupted.

Thus, looking at:

  e9d7144597b1 ("x86/cpu: Add a steppings field to struct x86_cpu_id")

for example, it doesn't have any text in there which hints at anything
NDA and so we can queue it for upstreaming now along with those below
and thus slim down the SRBDS queue even more. I.e., it will have only
three patches after this.

Thx.

---
From: Borislav Petkov <[email protected]>
Date: Tue, 5 May 2020 19:25:08 +0200
Subject: [PATCH 1/2] x86/cpu: Add a X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS() ma=
cro

... to match Intel family 6 CPUs with steppings.

Signed-off-by: Borislav Petkov <[email protected]>
---
 arch/x86/include/asm/cpu_device_id.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_=
device_id.h
index 10426cd56dca..eb8fcede9e3b 100644
--- a/arch/x86/include/asm/cpu_device_id.h
+++ b/arch/x86/include/asm/cpu_device_id.h
@@ -160,6 +160,10 @@
 #define X86_MATCH_INTEL_FAM6_MODEL(model, data)				\
 	X86_MATCH_VENDOR_FAM_MODEL(INTEL, 6, INTEL_FAM6_##model, data)
=20
+#define X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(model, steppings, data)	\
+	X86_MATCH_VENDOR_FAM_MODEL_STEPPINGS_FEATURE(INTEL, 6, INTEL_FAM6_##model, \
+						     steppings, X86_FEATURE_ANY, data)
+
 /*
  * Match specific microcode revisions.
  *
--=20
2.21.0

---
From: Borislav Petkov <[email protected]>
Date: Tue, 5 May 2020 19:27:16 +0200
Subject: [PATCH 2/2] x86/apic: Convert the TSC deadline timer matching to ste=
ppings macro

... and get rid of the function pointers which would spit out the
microcode revision based on the CPU stepping.

Signed-off-by: Borislav Petkov <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
---
 arch/x86/kernel/apic/apic.c | 57 ++++++++-----------------------------
 1 file changed, 12 insertions(+), 45 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index e53dda210cd7..4b1d31be50b4 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -544,46 +544,20 @@ static struct clock_event_device lapic_clockevent =3D {
 };
 static DEFINE_PER_CPU(struct clock_event_device, lapic_events);
=20
-static __init u32 hsx_deadline_rev(void)
-{
-	switch (boot_cpu_data.x86_stepping) {
-	case 0x02: return 0x3a; /* EP */
-	case 0x04: return 0x0f; /* EX */
-	}
-
-	return ~0U;
-}
-
-static __init u32 bdx_deadline_rev(void)
-{
-	switch (boot_cpu_data.x86_stepping) {
-	case 0x02: return 0x00000011;
-	case 0x03: return 0x0700000e;
-	case 0x04: return 0x0f00000c;
-	case 0x05: return 0x0e000003;
-	}
-
-	return ~0U;
-}
-
-static __init u32 skx_deadline_rev(void)
-{
-	switch (boot_cpu_data.x86_stepping) {
-	case 0x03: return 0x01000136;
-	case 0x04: return 0x02000014;
-	}
+static const struct x86_cpu_id deadline_match[] __initconst =3D {
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(HASWELL_X, X86_STEPPINGS(0x2, 0x2), 0x=
3a), /* EP */
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(HASWELL_X, X86_STEPPINGS(0x4, 0x4), 0x=
0f), /* EX */
=20
-	if (boot_cpu_data.x86_stepping > 4)
-		return 0;
+	X86_MATCH_INTEL_FAM6_MODEL( BROADWELL_X,	0x0b000020),
=20
-	return ~0U;
-}
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(BROADWELL_D, X86_STEPPINGS(0x2, 0x2), =
0x00000011),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(BROADWELL_D, X86_STEPPINGS(0x3, 0x3), =
0x0700000e),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(BROADWELL_D, X86_STEPPINGS(0x4, 0x4), =
0x0f00000c),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(BROADWELL_D, X86_STEPPINGS(0x5, 0x5), =
0x0e000003),
=20
-static const struct x86_cpu_id deadline_match[] __initconst =3D {
-	X86_MATCH_INTEL_FAM6_MODEL( HASWELL_X,		&hsx_deadline_rev),
-	X86_MATCH_INTEL_FAM6_MODEL( BROADWELL_X,	0x0b000020),
-	X86_MATCH_INTEL_FAM6_MODEL( BROADWELL_D,	&bdx_deadline_rev),
-	X86_MATCH_INTEL_FAM6_MODEL( SKYLAKE_X,		&skx_deadline_rev),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x3, 0x3), 0x=
01000136),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x4, 0x4), 0x=
02000014),
+	X86_MATCH_INTEL_FAM6_MODEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x5, 0xf), 0),
=20
 	X86_MATCH_INTEL_FAM6_MODEL( HASWELL,		0x22),
 	X86_MATCH_INTEL_FAM6_MODEL( HASWELL_L,		0x20),
@@ -615,14 +589,7 @@ static __init bool apic_validate_deadline_timer(void)
 	if (!m)
 		return true;
=20
-	/*
-	 * Function pointers will have the MSB set due to address layout,
-	 * immediate revisions will not.
-	 */
-	if ((long)m->driver_data < 0)
-		rev =3D ((u32 (*)(void))(m->driver_data))();
-	else
-		rev =3D (u32)m->driver_data;
+	rev =3D (u32)m->driver_data;
=20
 	if (boot_cpu_data.microcode >=3D rev)
 		return true;
--=20
2.21.0

--=20
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Felix Imend=C3=B6rffer, HRB 36809, =
AG N=C3=BCrnberg