96 lines
3.7 KiB
Diff
96 lines
3.7 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
|
|
From: Jiri Kosina <jkosina@suse.cz>
|
|
Date: Wed, 29 Aug 2018 19:17:40 +0000
|
|
Subject: [PATCH] x86/speculation: Protect against userspace-userspace
|
|
spectreRSB
|
|
|
|
The article "Spectre Returns! Speculation Attacks using the Return Stack
|
|
Buffer" [1] describes two new (sub-)variants of spectrev2-like attacks,
|
|
making use solely of the RSB contents even on CPUs that don't fallback to
|
|
BTB on RSB underflow (Skylake+).
|
|
|
|
Mitigate userspace-userspace attacks by always unconditionally filling RSB on
|
|
context switch when the generic spectrev2 mitigation has been enabled.
|
|
|
|
[1] https://arxiv.org/pdf/1807.07940.pdf
|
|
|
|
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
|
|
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
|
|
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
|
|
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
|
|
Cc: Borislav Petkov <bp@suse.de>
|
|
Cc: David Woodhouse <dwmw@amazon.co.uk>
|
|
Cc: Peter Zijlstra <peterz@infradead.org>
|
|
Cc: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Cc: stable@vger.kernel.org
|
|
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1807261308190.997@cbobk.fhfr.pm
|
|
|
|
CVE-2017-5715 (SpectreRSB sub-variant)
|
|
|
|
(cherry picked from commit fdf82a7856b32d905c39afc85e34364491e46346)
|
|
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
|
|
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
|
|
---
|
|
arch/x86/kernel/cpu/bugs.c | 38 +++++++-------------------------------
|
|
1 file changed, 7 insertions(+), 31 deletions(-)
|
|
|
|
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
|
|
index 700b4c0a93a2..edfc64a8a154 100644
|
|
--- a/arch/x86/kernel/cpu/bugs.c
|
|
+++ b/arch/x86/kernel/cpu/bugs.c
|
|
@@ -322,23 +322,6 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
|
|
return cmd;
|
|
}
|
|
|
|
-/* Check for Skylake-like CPUs (for RSB handling) */
|
|
-static bool __init is_skylake_era(void)
|
|
-{
|
|
- if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
|
|
- boot_cpu_data.x86 == 6) {
|
|
- switch (boot_cpu_data.x86_model) {
|
|
- case INTEL_FAM6_SKYLAKE_MOBILE:
|
|
- case INTEL_FAM6_SKYLAKE_DESKTOP:
|
|
- case INTEL_FAM6_SKYLAKE_X:
|
|
- case INTEL_FAM6_KABYLAKE_MOBILE:
|
|
- case INTEL_FAM6_KABYLAKE_DESKTOP:
|
|
- return true;
|
|
- }
|
|
- }
|
|
- return false;
|
|
-}
|
|
-
|
|
static void __init spectre_v2_select_mitigation(void)
|
|
{
|
|
enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
|
|
@@ -399,22 +382,15 @@ static void __init spectre_v2_select_mitigation(void)
|
|
pr_info("%s\n", spectre_v2_strings[mode]);
|
|
|
|
/*
|
|
- * If neither SMEP nor PTI are available, there is a risk of
|
|
- * hitting userspace addresses in the RSB after a context switch
|
|
- * from a shallow call stack to a deeper one. To prevent this fill
|
|
- * the entire RSB, even when using IBRS.
|
|
+ * If spectre v2 protection has been enabled, unconditionally fill
|
|
+ * RSB during a context switch; this protects against two independent
|
|
+ * issues:
|
|
*
|
|
- * Skylake era CPUs have a separate issue with *underflow* of the
|
|
- * RSB, when they will predict 'ret' targets from the generic BTB.
|
|
- * The proper mitigation for this is IBRS. If IBRS is not supported
|
|
- * or deactivated in favour of retpolines the RSB fill on context
|
|
- * switch is required.
|
|
+ * - RSB underflow (and switch to BTB) on Skylake+
|
|
+ * - SpectreRSB variant of spectre v2 on X86_BUG_SPECTRE_V2 CPUs
|
|
*/
|
|
- if ((!boot_cpu_has(X86_FEATURE_PTI) &&
|
|
- !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
|
|
- setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
|
|
- pr_info("Spectre v2 mitigation: Filling RSB on context switch\n");
|
|
- }
|
|
+ setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
|
|
+ pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n");
|
|
|
|
/* Initialize Indirect Branch Prediction Barrier if supported */
|
|
if (boot_cpu_has(X86_FEATURE_IBPB)) {
|