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feat: add detection of RSBA feature bit and adjust logic accordingly

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This commit is contained in:
Stéphane Lesimple 2018-08-09 21:03:58 +02:00
parent 860023a806
commit 4747b932e7
1 changed files with 29 additions and 5 deletions
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34
spectre-meltdown-checker.sh
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@ -1210,6 +1210,17 @@ is_skylake_cpu()
return 1
}
is_vulnerable_to_empty_rsb()
{
if [ -z "$capabilities_rsba" ]; then
_warn "is_vulnerable_to_empty_rsb() called before ARCH CAPABILITIES MSR was read"
fi
if is_skylake_cpu || [ "$capabilities_rsba" = 1 ]; then
return 0
fi
return 1
}
is_zen_cpu()
{
# is this CPU from the AMD ZEN family ? (ryzen, epyc, ...)
@ -1857,12 +1868,14 @@ check_cpu()
capabilities_rdcl_no=-1
capabilities_ibrs_all=-1
capabilities_ssb_no=-1
capabilities_rsba=-1
if [ "$cpuid_arch_capabilities" = -1 ]; then
pstatus yellow UNKNOWN
elif [ "$cpuid_arch_capabilities" != 1 ]; then
capabilities_rdcl_no=0
capabilities_ibrs_all=0
capabilities_ssb_no=0
capabilities_rsba=0
pstatus yellow NO
elif [ ! -e /dev/cpu/0/msr ] && [ ! -e /dev/cpuctl0 ]; then
spec_ctrl_msr=-1
@ -1892,12 +1905,14 @@ check_cpu()
capabilities_rdcl_no=0
capabilities_ibrs_all=0
capabilities_ssb_no=0
capabilities_rsba=0
if [ $val -eq 0 ]; then
_debug "capabilities MSR is $capabilities (decimal)"
[ $(( capabilities >> 0 & 1 )) -eq 1 ] && capabilities_rdcl_no=1
[ $(( capabilities >> 1 & 1 )) -eq 1 ] && capabilities_ibrs_all=1
[ $(( capabilities >> 2 & 1 )) -eq 1 ] && capabilities_rsba=1
[ $(( capabilities >> 4 & 1 )) -eq 1 ] && capabilities_ssb_no=1
_debug "capabilities says rdcl_no=$capabilities_rdcl_no ibrs_all=$capabilities_ibrs_all ssb_no=$capabilities_ssb_no"
_debug "capabilities says rdcl_no=$capabilities_rdcl_no ibrs_all=$capabilities_ibrs_all ssb_no=$capabilities_ssb_no rsba=$capabilities_rsba"
if [ "$capabilities_ibrs_all" = 1 ]; then
if [ $cpu_mismatch -eq 0 ]; then
pstatus green YES
@ -1935,6 +1950,15 @@ check_cpu()
pstatus yellow NO
fi
_info_nol " * Hypervisor indicates host CPU might be vulnerable to RSB underflow (RSBA): "
if [ "$capabilities_rsba" = -1 ]; then
pstatus yellow UNKNOWN
elif [ "$capabilities_rsba" = 1 ]; then
pstatus yellow YES
else
pstatus blue NO
fi
_info_nol " * CPU microcode is known to cause stability problems: "
if is_ucode_blacklisted; then
pstatus red YES "$ucode_found"
@ -2556,7 +2580,7 @@ check_variant2_linux()
fi
fi
if is_skylake_cpu || [ "$opt_verbose" -ge 2 ]; then
if is_vulnerable_to_empty_rsb || [ "$opt_verbose" -ge 2 ]; then
_info_nol " * Kernel supports RSB filling: "
if ! which "${opt_arch_prefix}strings" >/dev/null 2>&1; then
pstatus yellow UNKNOWN "missing '${opt_arch_prefix}strings' tool, please install it, usually it's in the binutils package"
@ -2583,9 +2607,9 @@ check_variant2_linux()
# override status & msg in case CPU is not vulnerable after all
pvulnstatus $cve OK "your CPU vendor reported your CPU model as not vulnerable"
else
if [ "$retpoline" = 1 ] && [ "$retpoline_compiler" = 1 ] && [ "$retp_enabled" != 0 ] && [ -n "$ibpb_enabled" ] && [ "$ibpb_enabled" -ge 1 ] && ( ! is_skylake_cpu || [ -n "$rsb_filling" ] ); then
if [ "$retpoline" = 1 ] && [ "$retpoline_compiler" = 1 ] && [ "$retp_enabled" != 0 ] && [ -n "$ibpb_enabled" ] && [ "$ibpb_enabled" -ge 1 ] && ( ! is_vulnerable_to_empty_rsb || [ -n "$rsb_filling" ] ); then
pvulnstatus $cve OK "Full retpoline + IBPB are mitigating the vulnerability"
elif [ "$retpoline" = 1 ] && [ "$retpoline_compiler" = 1 ] && [ "$retp_enabled" != 0 ] && [ "$opt_paranoid" = 0 ] && ( ! is_skylake_cpu || [ -n "$rsb_filling" ] ); then
elif [ "$retpoline" = 1 ] && [ "$retpoline_compiler" = 1 ] && [ "$retp_enabled" != 0 ] && [ "$opt_paranoid" = 0 ] && ( ! is_vulnerable_to_empty_rsb || [ -n "$rsb_filling" ] ); then
pvulnstatus $cve OK "Full retpoline is mitigating the vulnerability"
if [ -n "$cpuid_ibpb" ]; then
_warn "You should enable IBPB to complete retpoline as a Variant 2 mitigation"
@ -2615,7 +2639,7 @@ check_variant2_linux()
# if we arrive here and didn't already call pvulnstatus, then it's VULN, let's explain why
if [ "$pvulnstatus_last_cve" != "$cve" ]; then
# explain what's needed for this CPU
if is_skylake_cpu; then
if is_vulnerable_to_empty_rsb; then
pvulnstatus $cve VULN "IBRS+IBPB or retpoline+IBPB+RBS filling, is needed to mitigate the vulnerability"
explain "To mitigate this vulnerability, you need either IBRS + IBPB, both requiring hardware support from your CPU microcode in addition to kernel support, or a kernel compiled with retpoline and IBPB, with retpoline requiring a retpoline-aware compiler (re-run this script with -v to know if your version of gcc is retpoline-aware) and IBPB requiring hardware support from your CPU microcode. You also need a recent-enough kernel that supports RSB filling if you plan to use retpoline. For Skylake+ CPUs, the IBRS + IBPB approach is generally preferred as it guarantees complete protection, and the performance impact is not as high as with older CPUs in comparison with retpoline. More information about how to enable the missing bits for those two possible mitigations on your system follow. You only need to take one of the two approaches."
elif is_zen_cpu; then