[SRU][J][PATCH 2/8] x86/vmscape: Enumerate VMSCAPE bug
Massimiliano Pellizzer
massimiliano.pellizzer at canonical.com
Wed Sep 17 12:22:56 UTC 2025
From: Pawan Gupta <pawan.kumar.gupta at linux.intel.com>
BugLink: https://bugs.launchpad.net/bugs/2124105
commit a508cec6e5215a3fbc7e73ae86a5c5602187934d upstream.
The VMSCAPE vulnerability may allow a guest to cause Branch Target
Injection (BTI) in userspace hypervisors.
Kernels (both host and guest) have existing defenses against direct BTI
attacks from guests. There are also inter-process BTI mitigations which
prevent processes from attacking each other. However, the threat in this
case is to a userspace hypervisor within the same process as the attacker.
Userspace hypervisors have access to their own sensitive data like disk
encryption keys and also typically have access to all guest data. This
means guest userspace may use the hypervisor as a confused deputy to attack
sensitive guest kernel data. There are no existing mitigations for these
attacks.
Introduce X86_BUG_VMSCAPE for this vulnerability and set it on affected
Intel and AMD CPUs.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta at linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen at linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp at alien8.de>
[Amit:
* Drop unsupported Intel families: ARROWLAKE, METEORLAKE,
ATOM_CRESTMONT_X; and unlisted ATOM types for RAPTORLAKE and
ALDERLAKE
* s/ATOM_GRACEMONT/ALDERLAKE_N/
* Drop unsupported AMD family: 0x1a]
Signed-off-by: Amit Shah <amit.shah at amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit f2ed886bb650423b5a1e0478f5d4349fdc576d7f linux-5.15.y)
CVE-2025-40300
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kernel/cpu/common.c | 56 +++++++++++++++++++-----------
2 files changed, 36 insertions(+), 21 deletions(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 2720c86d722ec..3732b5b5b067f 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -497,4 +497,5 @@
#define X86_BUG_ITS X86_BUG(1*32 + 5) /* CPU is affected by Indirect Target Selection */
#define X86_BUG_ITS_NATIVE_ONLY X86_BUG(1*32 + 6) /* CPU is affected by ITS, VMX is not affected */
#define X86_BUG_TSA X86_BUG(1*32+ 9) /* "tsa" CPU is affected by Transient Scheduler Attacks */
+#define X86_BUG_VMSCAPE X86_BUG(1*32+10) /* "vmscape" CPU is affected by VMSCAPE attacks from guests */
#endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4c4d3a7a8c075..6781b66963c87 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1221,6 +1221,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
#define ITS_NATIVE_ONLY BIT(9)
/* CPU is affected by Transient Scheduler Attacks */
#define TSA BIT(10)
+/* CPU is affected by VMSCAPE */
+#define VMSCAPE BIT(11)
static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
@@ -1232,31 +1234,35 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(BROADWELL_G, X86_STEPPING_ANY, SRBDS),
VULNBL_INTEL_STEPPINGS(BROADWELL_X, X86_STEPPING_ANY, MMIO),
VULNBL_INTEL_STEPPINGS(BROADWELL, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x0, 0x5), MMIO | RETBLEED | GDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPINGS(0x0, 0xb), MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPINGS(0x0, 0xc), MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS),
- VULNBL_INTEL_STEPPINGS(CANNONLAKE_L, X86_STEPPING_ANY, RETBLEED),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x0, 0x5), MMIO | RETBLEED | GDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPINGS(0x0, 0xb), MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPINGS(0x0, 0xc), MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(CANNONLAKE_L, X86_STEPPING_ANY, RETBLEED | VMSCAPE),
VULNBL_INTEL_STEPPINGS(ICELAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(ICELAKE_D, X86_STEPPING_ANY, MMIO | GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(ICELAKE_X, X86_STEPPING_ANY, MMIO | GDS | ITS | ITS_NATIVE_ONLY),
- VULNBL_INTEL_STEPPINGS(COMETLAKE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
- VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPINGS(0x0, 0x0), MMIO | RETBLEED | ITS),
- VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPINGS(0x0, 0x0), MMIO | RETBLEED | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
VULNBL_INTEL_STEPPINGS(TIGERLAKE_L, X86_STEPPING_ANY, GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(TIGERLAKE, X86_STEPPING_ANY, GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(LAKEFIELD, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED),
VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE_N, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_N, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(LUNARLAKE_M, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SAPPHIRERAPIDS_X,X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(GRANITERAPIDS_X, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(EMERALDRAPIDS_X, X86_STEPPING_ANY, VMSCAPE),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO | RFDS),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
@@ -1266,9 +1272,9 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_AMD(0x15, RETBLEED),
VULNBL_AMD(0x16, RETBLEED),
- VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO),
- VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO),
- VULNBL_AMD(0x19, SRSO | TSA),
+ VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_AMD(0x19, SRSO | TSA | VMSCAPE),
{}
};
@@ -1483,6 +1489,14 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
}
}
+ /*
+ * Set the bug only on bare-metal. A nested hypervisor should already be
+ * deploying IBPB to isolate itself from nested guests.
+ */
+ if (cpu_matches(cpu_vuln_blacklist, VMSCAPE) &&
+ !boot_cpu_has(X86_FEATURE_HYPERVISOR))
+ setup_force_cpu_bug(X86_BUG_VMSCAPE);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;
--
2.48.1
More information about the kernel-team
mailing list