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enh: CVE-2022-40982 (Downfall) overhaul
built from commit c4c4ea8c0a5f2ffde852a22f26b9801bca61139a dated 2026-04-02 19:55:25 +0200 by Stéphane Lesimple (speed47_github@speed47.net) - added `--kernel-config` support for all three Kconfig variants seen over all kernel versions up to now - added `--kernel-map` support for `gds_select_mitigation` in `System.map` - fixed the `--sysfs-only` mode - added verbose information about remediation when `--explain` is used - implemented `--paranoid mode`, requiring `GDS_MITIGATION_LOCKED` so that mitigation can't be disabled at runtime - fixed offline mode (was wrongly looking at the system `dmesg`) - better microcode status reporting (enabled, disabled, unsupported, unknown) - fixed unknown (EOL) AVX-capable Intel family 6 CPUs now defaulting to affected - fixed 2 missing known affected CPU models: INTEL_FAM6_SKYLAKE_L and INTEL_FAM6_SKYLAKE
This commit is contained in:
github-actions[bot]
@@ -13,7 +13,7 @@
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#
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# Stephane Lesimple
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#
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VERSION='26.21.0402699'
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VERSION='26.21.0402751'
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# --- Common paths and basedirs ---
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readonly VULN_SYSFS_BASE="/sys/devices/system/cpu/vulnerabilities"
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@@ -588,9 +588,12 @@ is_cpu_affected() {
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pr_debug "is_cpu_affected: downfall: not affected (GDS_NO)"
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_set_immune downfall
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elif [ "$cpu_family" = 6 ]; then
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# list from https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=64094e7e3118aff4b0be8ff713c242303e139834
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# model blacklist from the kernel (arch/x86/kernel/cpu/common.c cpu_vuln_blacklist):
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# 8974eb588283 (initial list) + c9f4c45c8ec3 (added Skylake/Skylake_L client)
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set -u
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if [ "$cpu_model" = "$INTEL_FAM6_SKYLAKE_X" ] ||
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if [ "$cpu_model" = "$INTEL_FAM6_SKYLAKE_L" ] ||
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[ "$cpu_model" = "$INTEL_FAM6_SKYLAKE" ] ||
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[ "$cpu_model" = "$INTEL_FAM6_SKYLAKE_X" ] ||
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[ "$cpu_model" = "$INTEL_FAM6_KABYLAKE_L" ] ||
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[ "$cpu_model" = "$INTEL_FAM6_KABYLAKE" ] ||
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[ "$cpu_model" = "$INTEL_FAM6_ICELAKE_L" ] ||
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@@ -605,10 +608,12 @@ is_cpu_affected() {
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_set_vuln downfall
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elif [ "$cap_avx2" = 0 ] && [ "$cap_avx512" = 0 ]; then
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pr_debug "is_cpu_affected: downfall: no avx; immune"
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_infer_immune downfall
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else
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# old Intel CPU (not in their DB), not listed as being affected by the Linux kernel,
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# but with AVX2 or AVX512: unclear for now
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pr_debug "is_cpu_affected: downfall: unclear, defaulting to non-affected for now"
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# Intel family 6 CPU with AVX2 or AVX512, not in the known-affected list
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# and GDS_NO not set: assume affected (whitelist principle)
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pr_debug "is_cpu_affected: downfall: unknown AVX-capable CPU, defaulting to affected"
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_infer_vuln downfall
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fi
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set +u
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fi
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@@ -7475,6 +7480,90 @@ check_CVE_2022_40982_linux() {
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if sys_interface_check "$VULN_SYSFS_BASE/gather_data_sampling"; then
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# this kernel has the /sys interface, trust it over everything
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sys_interface_available=1
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#
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# Kernel source inventory for gather_data_sampling (GDS/Downfall)
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#
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# --- sysfs messages ---
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# all versions:
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# "Not affected" (cpu_show_common, pre-existing)
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#
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# --- mainline ---
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# 8974eb588283 (v6.5-rc6, initial GDS sysfs):
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# "Vulnerable" (GDS_MITIGATION_OFF)
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# "Vulnerable: No microcode" (GDS_MITIGATION_UCODE_NEEDED)
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# "Mitigation: Microcode" (GDS_MITIGATION_FULL)
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# "Mitigation: Microcode (locked)" (GDS_MITIGATION_FULL_LOCKED)
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# "Unknown: Dependent on hypervisor status" (GDS_MITIGATION_HYPERVISOR)
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# 553a5c03e90a (v6.5-rc6, added force option):
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# "Mitigation: AVX disabled, no microcode" (GDS_MITIGATION_FORCE)
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# 53cf5797f114 (v6.5-rc6, added CONFIG_GDS_FORCE_MITIGATION):
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# no string changes; default becomes FORCE when Kconfig enabled
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# 81ac7e5d7417 (v6.5-rc6, KVM GDS_NO plumbing):
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# no string changes
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# be83e809ca67 (v6.9-rc1, Kconfig rename):
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# no string changes; CONFIG_GDS_FORCE_MITIGATION => CONFIG_MITIGATION_GDS_FORCE
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# 03267a534bb3 (v6.12-rc1, removed force Kconfig):
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# no string changes; CONFIG_MITIGATION_GDS_FORCE removed
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# 225f2bd064c3 (v6.12-rc1, added on/off Kconfig):
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# no string changes; added CONFIG_MITIGATION_GDS (default y)
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# 9dcad2fb31bd (v6.16-rc1, restructured select/apply):
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# no string changes; added GDS_MITIGATION_AUTO (internal, resolved before display)
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# split gds_select_mitigation() + gds_apply_mitigation()
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# d4932a1b148b (v6.17-rc3, bug fix):
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# no string changes; CPUs without ARCH_CAP_GDS_CTRL were incorrectly classified
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# as OFF ("Vulnerable") instead of UCODE_NEEDED ("Vulnerable: No microcode"),
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# and locked-mitigation detection was skipped.
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# NOT backported to any stable or RHEL branch as of 2026-04.
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#
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# --- stable backports ---
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# 5.4.y, 5.10.y, 5.15.y, 6.1.y, 6.6.y: same 7 strings as mainline.
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# use CONFIG_GDS_FORCE_MITIGATION; no GDS_MITIGATION_AUTO enum;
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# missing d4932a1b148b bug fix (UCODE_NEEDED vs OFF misclassification).
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# 6.12.y: same 7 strings as mainline.
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# uses CONFIG_MITIGATION_GDS; no GDS_MITIGATION_AUTO enum;
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# missing d4932a1b148b bug fix.
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#
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# --- RHEL/CentOS ---
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# centos7 (3.10), rocky8 (4.18): same 7 strings; CONFIG_GDS_FORCE_MITIGATION.
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# centos7 uses sprintf (not sysfs_emit) and __read_mostly.
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# rocky9 (5.14): same 7 strings; CONFIG_MITIGATION_GDS (skipped FORCE rename).
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# rocky10 (6.12): same 7 strings; CONFIG_MITIGATION_GDS; has gds_apply_mitigation().
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#
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# --- Kconfig symbols ---
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# 53cf5797f114 (v6.5-rc6): CONFIG_GDS_FORCE_MITIGATION (default n)
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# be83e809ca67 (v6.9-rc1): renamed to CONFIG_MITIGATION_GDS_FORCE
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# 03267a534bb3 (v6.12-rc1): CONFIG_MITIGATION_GDS_FORCE removed
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# 225f2bd064c3 (v6.12-rc1): CONFIG_MITIGATION_GDS (default y)
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# vendor kernels: rocky9 uses CONFIG_MITIGATION_GDS on 5.14-based kernel
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#
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# --- kernel functions (for $opt_map / System.map) ---
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# 8974eb588283 (v6.5-rc6): gds_select_mitigation(), update_gds_msr(),
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# gds_parse_cmdline(), gds_show_state()
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# 81ac7e5d7417 (v6.5-rc6): gds_ucode_mitigated() (exported for KVM)
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# 9dcad2fb31bd (v6.16-rc1): split into gds_select_mitigation() + gds_apply_mitigation()
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# stable 5.4.y-6.12.y: same 5 functions (no gds_apply_mitigation)
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# rocky10 (6.12): has gds_apply_mitigation()
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#
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# --- CPU affection logic (for is_cpu_affected) ---
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# X86_BUG_GDS is set when ALL three conditions are true:
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# 1. CPU matches model blacklist (cpu_vuln_blacklist[] in common.c)
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# 2. ARCH_CAP_GDS_NO (bit 26 of IA32_ARCH_CAPABILITIES) is NOT set
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# 3. X86_FEATURE_AVX is present (GATHER instructions require AVX)
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# 8974eb588283 (v6.5-rc6, initial model list):
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# Intel: SKYLAKE_X, KABYLAKE_L, KABYLAKE, ICELAKE_L, ICELAKE_D,
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# ICELAKE_X, COMETLAKE, COMETLAKE_L, TIGERLAKE_L, TIGERLAKE,
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# ROCKETLAKE (all steppings)
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# c9f4c45c8ec3 (v6.5-rc6, added missing client Skylake):
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# Intel: + SKYLAKE_L, SKYLAKE
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# 159013a7ca18 (v6.10-rc1, ITS stepping splits):
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# no GDS model changes; some entries split by stepping for ITS but
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# GDS flag remains on all stepping ranges for these models
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# immunity: ARCH_CAP_GDS_NO (bit 26 of IA32_ARCH_CAPABILITIES)
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# feature dependency: requires AVX (if AVX absent, CPU is immune)
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# vendor scope: Intel only
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#
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# all messages start with either "Not affected", "Vulnerable", "Mitigation",
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# or "Unknown"
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status=$ret_sys_interface_check_status
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fi
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@@ -7482,15 +7571,34 @@ check_CVE_2022_40982_linux() {
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pr_info_nol "* GDS is mitigated by microcode: "
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if [ "$cap_gds_ctrl" = 1 ] && [ "$cap_gds_mitg_dis" = 0 ]; then
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pstatus green OK "microcode mitigation is supported and enabled"
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elif [ "$cap_gds_ctrl" = 1 ] && [ "$cap_gds_mitg_dis" = 1 ]; then
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pstatus yellow NO "microcode mitigation is supported but disabled"
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elif [ "$cap_gds_ctrl" = 0 ]; then
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pstatus yellow NO "microcode doesn't support GDS mitigation"
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else
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pstatus yellow NO
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pstatus yellow UNKNOWN "couldn't read MSR for GDS capability"
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fi
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pr_info_nol "* Kernel supports software mitigation by disabling AVX: "
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kernel_gds=''
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kernel_gds_err=''
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if [ -n "$g_kernel_err" ]; then
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kernel_gds_err="$g_kernel_err"
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elif grep -q 'gather_data_sampling' "$g_kernel"; then
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kernel_gds="found gather_data_sampling in kernel image"
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fi
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if [ -z "$kernel_gds" ] && [ -r "$opt_config" ]; then
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if grep -q '^CONFIG_GDS_FORCE_MITIGATION=y' "$opt_config" ||
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grep -q '^CONFIG_MITIGATION_GDS_FORCE=y' "$opt_config" ||
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grep -q '^CONFIG_MITIGATION_GDS=y' "$opt_config"; then
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kernel_gds="GDS mitigation config option found enabled in kernel config"
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fi
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fi
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if [ -z "$kernel_gds" ] && [ -n "$opt_map" ]; then
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if grep -q 'gds_select_mitigation' "$opt_map"; then
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kernel_gds="found gds_select_mitigation in System.map"
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fi
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fi
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if [ -n "$kernel_gds" ]; then
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pstatus green YES "$kernel_gds"
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elif [ -n "$kernel_gds_err" ]; then
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@@ -7502,6 +7610,7 @@ check_CVE_2022_40982_linux() {
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if [ -n "$kernel_gds" ]; then
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pr_info_nol "* Kernel has disabled AVX as a mitigation: "
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if [ "$opt_live" = 1 ]; then
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# Check dmesg message to see whether AVX has been disabled
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dmesg_grep 'Microcode update needed! Disabling AVX as mitigation'
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dmesgret=$?
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@@ -7527,6 +7636,9 @@ check_CVE_2022_40982_linux() {
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else
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pstatus yellow NO "AVX support is enabled"
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fi
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else
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pstatus blue N/A "not testable in offline mode"
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fi
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fi
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elif [ "$sys_interface_available" = 0 ]; then
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@@ -7540,17 +7652,34 @@ check_CVE_2022_40982_linux() {
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pvulnstatus "$cve" OK "your CPU vendor reported your CPU model as not affected"
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elif [ -z "$msg" ]; then
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# if msg is empty, sysfs check didn't fill it, rely on our own test
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if [ "$opt_sysfs_only" != 1 ]; then
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if [ "$cap_gds_ctrl" = 1 ] && [ "$cap_gds_mitg_dis" = 0 ]; then
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if [ "$opt_paranoid" = 1 ] && [ "$cap_gds_mitg_lock" != 1 ]; then
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pvulnstatus "$cve" VULN "Microcode mitigation is enabled but not locked"
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explain "In paranoid mode, the GDS mitigation must be locked to prevent a privileged attacker\n " \
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"(e.g. in a guest VM) from disabling it. Check your firmware/BIOS for an option to lock the\n " \
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"GDS mitigation, or update your microcode."
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else
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pvulnstatus "$cve" OK "Your microcode is up to date and mitigation is enabled"
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fi
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elif [ "$cap_gds_ctrl" = 1 ] && [ "$cap_gds_mitg_dis" = 1 ]; then
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pvulnstatus "$cve" VULN "Your microcode is up to date but mitigation is disabled"
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explain "The GDS mitigation has been explicitly disabled (gather_data_sampling=off or mitigations=off).\n " \
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"Remove the kernel parameter to re-enable it."
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elif [ -z "$kernel_gds" ]; then
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pvulnstatus "$cve" VULN "Your microcode doesn't mitigate the vulnerability, and your kernel doesn't support mitigation"
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explain "Update both your CPU microcode (via BIOS/firmware update from your OEM) and your kernel\n " \
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"to a version that supports GDS mitigation (Linux 6.5+, or check if your distro has a backport)."
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elif [ -z "$kernel_avx_disabled" ]; then
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pvulnstatus "$cve" VULN "Your microcode doesn't mitigate the vulnerability, your kernel support the mitigation but the script did not detect AVX as disabled by the kernel"
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pvulnstatus "$cve" VULN "Your microcode doesn't mitigate the vulnerability, your kernel supports the mitigation but AVX was not disabled"
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explain "Update your CPU microcode (via BIOS/firmware update from your OEM). If no microcode update\n " \
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"is available, use gather_data_sampling=force on the kernel command line to disable AVX as a workaround."
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else
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pvulnstatus "$cve" OK "Your microcode doesn't mitigate the vulnerability, but your kernel has disabled AVX support"
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fi
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else
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pvulnstatus "$cve" "$status" "$ret_sys_interface_check_fullmsg"
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fi
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else
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pvulnstatus "$cve" "$status" "$msg"
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fi
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