Subject: Patch "arm64: add sysfs vulnerability show for spectre-v2" has been added to the 4.19-stable tree

From: <[email-masked]>
Date: Wed, 09 Oct 2019 10:04:01 +0200

This is a note to let you know that I've just added the patch titled

    arm64: add sysfs vulnerability show for spectre-v2

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-add-sysfs-vulnerability-show-for-spectre-v2.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <[email-masked]> know about it.

>From foo@baz Wed 09 Oct 2019 10:02:11 AM CEST
From: Ard Biesheuvel <[email-masked]>
Date: Tue,  8 Oct 2019 17:39:27 +0200
Subject: arm64: add sysfs vulnerability show for spectre-v2
To: [email-masked]
Cc: [email-masked], Jeremy Linton <[email-masked]>, Andre Przywara <[email-masked]>, Catalin Marinas <[email-masked]>, Stefan Wahren <[email-masked]>, Will Deacon <[email-masked]>, Ard Biesheuvel <[email-masked]>
Message-ID: <[email-masked]>

From: Jeremy Linton <[email-masked]>

[ Upstream commit d2532e27b5638bb2e2dd52b80b7ea2ec65135377 ]

Track whether all the cores in the machine are vulnerable to Spectre-v2,
and whether all the vulnerable cores have been mitigated. We then expose
this information to userspace via sysfs.

Signed-off-by: Jeremy Linton <[email-masked]>
Reviewed-by: Andre Przywara <[email-masked]>
Reviewed-by: Catalin Marinas <[email-masked]>
Tested-by: Stefan Wahren <[email-masked]>
Signed-off-by: Will Deacon <[email-masked]>
Signed-off-by: Ard Biesheuvel <[email-masked]>
Signed-off-by: Greg Kroah-Hartman <[email-masked]>
---
 arch/arm64/kernel/cpu_errata.c |   27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -480,6 +480,10 @@ has_cortex_a76_erratum_1463225(const str
 	.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,			\
 	CAP_MIDR_RANGE_LIST(midr_list)
 
+/* Track overall mitigation state. We are only mitigated if all cores are ok */
+static bool __hardenbp_enab = true;
+static bool __spectrev2_safe = true;
+
 /*
  * Generic helper for handling capabilties with multiple (match,enable) pairs
  * of call backs, sharing the same capability bit.
@@ -522,6 +526,10 @@ static const struct midr_range spectre_v
 	{ /* sentinel */ }
 };
 
+/*
+ * Track overall bp hardening for all heterogeneous cores in the machine.
+ * We are only considered "safe" if all booted cores are known safe.
+ */
 static bool __maybe_unused
 check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope)
 {
@@ -543,6 +551,8 @@ check_branch_predictor(const struct arm6
 	if (!need_wa)
 		return false;
 
+	__spectrev2_safe = false;
+
 	if (!IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR)) {
 		pr_warn_once("spectrev2 mitigation disabled by kernel configuration\n");
 		__hardenbp_enab = false;
@@ -552,11 +562,14 @@ check_branch_predictor(const struct arm6
 	/* forced off */
 	if (__nospectre_v2) {
 		pr_info_once("spectrev2 mitigation disabled by command line option\n");
+		__hardenbp_enab = false;
 		return false;
 	}
 
-	if (need_wa < 0)
+	if (need_wa < 0) {
 		pr_warn_once("ARM_SMCCC_ARCH_WORKAROUND_1 missing from firmware\n");
+		__hardenbp_enab = false;
+	}
 
 	return (need_wa > 0);
 }
@@ -753,3 +766,15 @@ ssize_t cpu_show_spectre_v1(struct devic
 {
 	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
 }
+
+ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	if (__spectrev2_safe)
+		return sprintf(buf, "Not affected\n");
+
+	if (__hardenbp_enab)
+		return sprintf(buf, "Mitigation: Branch predictor hardening\n");
+
+	return sprintf(buf, "Vulnerable\n");
+}

Patches currently in stable-queue which might be from [email-masked] are

queue-4.19/arm64-add-sysfs-vulnerability-show-for-meltdown.patch
queue-4.19/arm64-force-ssbs-on-context-switch.patch
queue-4.19/arm64-enable-generic-cpu-vulnerabilites-support.patch
queue-4.19/arm64-provide-a-command-line-to-disable-spectre_v2-mitigation.patch
queue-4.19/arm64-always-enable-spectre-v2-vulnerability-detection.patch
queue-4.19/arm64-docs-document-ssbs-hwcap.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-spectre-v1.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-speculative-store-bypass.patch
queue-4.19/kvm-arm64-set-sctlr_el2.dssbs-if-ssbd-is-forcefully-disabled-and-vhe.patch
queue-4.19/arm64-always-enable-ssb-vulnerability-detection.patch
queue-4.19/arm64-advertise-mitigation-of-spectre-v2-or-lack-thereof.patch
queue-4.19/arm64-ssbs-don-t-treat-cpus-with-ssbs-as-unaffected-by-ssb.patch
queue-4.19/crypto-skcipher-unmap-pages-after-an-external-error.patch
queue-4.19/arm64-cpufeature-detect-ssbs-and-advertise-to-userspace.patch
queue-4.19/arm64-ssbd-add-support-for-pstate.ssbs-rather-than-trapping-to-el3.patch
queue-4.19/arm64-fix-ssbs-sanitization.patch
queue-4.19/arm64-add-sysfs-vulnerability-show-for-spectre-v2.patch

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