[PATCH 5.15 42/78] x86/bugs: Report AMD retbleed vulnerability

Greg Kroah-Hartman
2022-07-12T19:03:19Z

From: Alexandre Chartre <alexandre.chartre@oracle.com>

commit 6b80b59b3555706508008f1f127b5412c89c7fd8 upstream.

Report that AMD x86 CPUs are vulnerable to the RETBleed (Arbitrary
Speculative Code Execution with Return Instructions) attack.

[peterz: add hygon]
[kim: invert parity; fam15h]

Co-developed-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kernel/cpu/bugs.c | 13 +++++++++++++
arch/x86/kernel/cpu/common.c | 19 +++++++++++++++++++
drivers/base/cpu.c | 8 ++++++++
include/linux/cpu.h | 2 ++
5 files changed, 43 insertions(+)

--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -443,5 +443,6 @@
#define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
#define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
#define X86_BUG_MMIO_STALE_DATA X86_BUG(25) /* CPU is affected by Processor MMIO Stale Data vulnerabilities */
+#define X86_BUG_RETBLEED X86_BUG(26) /* CPU is affected by RETBleed */

#endif /* _ASM_X86_CPUFEATURES_H */
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1987,6 +1987,11 @@ static ssize_t srbds_show_state(char *bu
return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
}

+static ssize_t retbleed_show_state(char *buf)
+{
+ return sprintf(buf, "Vulnerable\n");
+}
+
static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
char *buf, unsigned int bug)
{
@@ -2032,6 +2037,9 @@ static ssize_t cpu_show_common(struct de
case X86_BUG_MMIO_STALE_DATA:
return mmio_stale_data_show_state(buf);

+ case X86_BUG_RETBLEED:
+ return retbleed_show_state(buf);
+
default:
break;
}
@@ -2088,4 +2096,9 @@ ssize_t cpu_show_mmio_stale_data(struct
{
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
}
+
+ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED);
+}
#endif
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1095,16 +1095,27 @@ static const __initconst struct x86_cpu_
{}
};

+#define VULNBL(vendor, family, model, blacklist) \
+ X86_MATCH_VENDOR_FAM_MODEL(vendor, family, model, blacklist)
+
#define VULNBL_INTEL_STEPPINGS(model, steppings, issues) \
X86_MATCH_VENDOR_FAM_MODEL_STEPPINGS_FEATURE(INTEL, 6, \
INTEL_FAM6_##model, steppings, \
X86_FEATURE_ANY, issues)

+#define VULNBL_AMD(family, blacklist) \
+ VULNBL(AMD, family, X86_MODEL_ANY, blacklist)
+
+#define VULNBL_HYGON(family, blacklist) \
+ VULNBL(HYGON, family, X86_MODEL_ANY, blacklist)
+
#define SRBDS BIT(0)
/* CPU is affected by X86_BUG_MMIO_STALE_DATA */
#define MMIO BIT(1)
/* CPU is affected by Shared Buffers Data Sampling (SBDS), a variant of X86_BUG_MMIO_STALE_DATA */
#define MMIO_SBDS BIT(2)
+/* CPU is affected by RETbleed, speculating where you would not expect it */
+#define RETBLEED BIT(3)

static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
@@ -1137,6 +1148,11 @@ static const struct x86_cpu_id cpu_vuln_
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPINGS(0x1, 0x1), MMIO | MMIO_SBDS),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPINGS(0x0, 0x0), MMIO | MMIO_SBDS),
+
+ VULNBL_AMD(0x15, RETBLEED),
+ VULNBL_AMD(0x16, RETBLEED),
+ VULNBL_AMD(0x17, RETBLEED),
+ VULNBL_HYGON(0x18, RETBLEED),
{}
};

@@ -1238,6 +1254,9 @@ static void __init cpu_set_bug_bits(stru
!arch_cap_mmio_immune(ia32_cap))
setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA);

+ if (cpu_matches(cpu_vuln_blacklist, RETBLEED))
+ setup_force_cpu_bug(X86_BUG_RETBLEED);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;

--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -570,6 +570,12 @@ ssize_t __weak cpu_show_mmio_stale_data(
return sysfs_emit(buf, "Not affected\n");
}

+ssize_t __weak cpu_show_retbleed(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "Not affected\n");
+}
+
static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
@@ -580,6 +586,7 @@ static DEVICE_ATTR(tsx_async_abort, 0444
static DEVICE_ATTR(itlb_multihit, 0444, cpu_show_itlb_multihit, NULL);
static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL);
static DEVICE_ATTR(mmio_stale_data, 0444, cpu_show_mmio_stale_data, NULL);
+static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL);

static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@@ -592,6 +599,7 @@ static struct attribute *cpu_root_vulner
&dev_attr_itlb_multihit.attr,
&dev_attr_srbds.attr,
&dev_attr_mmio_stale_data.attr,
+ &dev_attr_retbleed.attr,
NULL
};

--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -68,6 +68,8 @@ extern ssize_t cpu_show_srbds(struct dev
extern ssize_t cpu_show_mmio_stale_data(struct device *dev,
struct device_attribute *attr,
char *buf);
+extern ssize_t cpu_show_retbleed(struct device *dev,
+ struct device_attribute *attr, char *buf);

extern __printf(4, 5)
struct device *cpu_device_create(struct device *parent, void *drvdata,