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fix: CPUs affected by MSBDS but not MDS (fix #351)

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built from commit 716caae53f8ee8a6276a8fa0b9327b3ee3f4a3e0
 dated 2026-04-06 12:58:03 +0200
 by Stéphane Lesimple (speed47_github@speed47.net)
This commit is contained in:
github-actions[bot]
2026-04-06 10:59:40 +00:00
parent fc66ee567a
commit d247733496
1 changed files with 50 additions and 1 deletions
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51
spectre-meltdown-checker.sh
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@@ -13,7 +13,7 @@
#
# Stephane Lesimple
#
VERSION='26.32.0406444'
VERSION='26.32.0406457'
# --- Common paths and basedirs ---
readonly VULN_SYSFS_BASE="/sys/devices/system/cpu/vulnerabilities"
@@ -614,6 +614,11 @@ is_cpu_affected() {
_infer_immune mlpds
_infer_immune mdsum
pr_debug "is_cpu_affected: cpu not affected by Microarchitectural Data Sampling"
elif is_cpu_msbds_only; then
_infer_immune mfbds
_infer_immune mlpds
_infer_immune mdsum
pr_debug "is_cpu_affected: cpu only affected by MSBDS, not MFBDS/MLPDS/MDSUM"
fi
if is_cpu_taa_free; then
@@ -1402,6 +1407,37 @@ is_cpu_mds_free() {
return 1
}
# Check whether the CPU is known to be affected by MSBDS only (not MFBDS/MLPDS/MDSUM)
# These CPUs have a different microarchitecture that is only susceptible to
# Microarchitectural Store Buffer Data Sampling, not the other MDS variants.
# Returns: 0 if MSBDS-only, 1 otherwise
is_cpu_msbds_only() {
# source: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/cpu/common.c
#VULNWL_INTEL(ATOM_SILVERMONT, MSBDS_ONLY),
#VULNWL_INTEL(ATOM_SILVERMONT_D, MSBDS_ONLY),
#VULNWL_INTEL(ATOM_SILVERMONT_MID, MSBDS_ONLY),
#VULNWL_INTEL(ATOM_SILVERMONT_MID2, MSBDS_ONLY),
#VULNWL_INTEL(ATOM_AIRMONT, MSBDS_ONLY),
#VULNWL_INTEL(XEON_PHI_KNL, MSBDS_ONLY),
#VULNWL_INTEL(XEON_PHI_KNM, MSBDS_ONLY),
parse_cpu_details
if is_intel; then
if [ "$cpu_family" = 6 ]; then
if [ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT" ] ||
[ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_D" ] ||
[ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_MID" ] ||
[ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_MID2" ] ||
[ "$cpu_model" = "$INTEL_FAM6_ATOM_AIRMONT" ] ||
[ "$cpu_model" = "$INTEL_FAM6_XEON_PHI_KNL" ] ||
[ "$cpu_model" = "$INTEL_FAM6_XEON_PHI_KNM" ]; then
return 0
fi
fi
fi
return 1
}
# Check whether the CPU is known to be unaffected by TSX Asynchronous Abort (TAA)
# Returns: 0 if TAA-free, 1 if affected or unknown
is_cpu_taa_free() {
@@ -2944,6 +2980,19 @@ read_msr_one_core() {
return "$(eval echo \$$mockvarname)"
fi
# proactive lockdown detection via sysfs (vanilla 5.4+, CentOS 8+, Rocky 9+):
# if the kernel lockdown is set to integrity or confidentiality, MSR writes will be denied,
# so we can skip the write attempt entirely and avoid relying on dmesg parsing
if [ -e "$SYSKERNEL_BASE/security/lockdown" ]; then
if grep -qE '\[integrity\]|\[confidentiality\]' "$SYSKERNEL_BASE/security/lockdown" 2>/dev/null; then
pr_debug "write_msr: kernel lockdown detected via $SYSKERNEL_BASE/security/lockdown"
g_mockme=$(printf "%b\n%b" "$g_mockme" "SMC_MOCK_WRMSR_${msr}_RET=$WRITE_MSR_RET_LOCKDOWN")
g_msr_locked_down=1
ret_write_msr_msg="your kernel is locked down, please reboot with lockdown=none in the kernel cmdline and retry"
return $WRITE_MSR_RET_LOCKDOWN
fi
fi
if [ ! -e $CPU_DEV_BASE/0/msr ] && [ ! -e ${BSD_CPUCTL_DEV_BASE}0 ]; then
# try to load the module ourselves (and remember it so we can rmmod it afterwards)
load_msr