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xen: detect if the host is a Xen Dom0 or PV DomU (fixes #83)

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Matthieu Cerda 2018-01-24 17:14:04 +01:00 committed by Stéphane Lesimple
parent d1c1f0f0f0
commit 7f0d80b305
1 changed files with 49 additions and 22 deletions
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71
spectre-meltdown-checker.sh
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@ -1456,31 +1456,39 @@ check_variant3()
pstatus blue NO 'no security impact but performance will be degraded with PTI'
fi
fi
if [ "$opt_live" = 1 ]; then
# checking whether we're running under Xen PV 64 bits. If yes, we're not affected by variant3
_info_nol "* Running under Xen PV (64 bits): "
if [ "$(uname -m)" = "x86_64" ]; then
# XXX do we have a better way that relying on dmesg?
dmesg_grep 'Booting paravirtualized kernel on Xen$'; ret=$?
if [ $ret -eq 0 ]; then
pstatus green YES 'Xen PV is not vulnerable'
xen_pv=1
elif [ $ret -eq 2 ]; then
pstatus yellow UNKNOWN "dmesg truncated, please reboot and relaunch this script"
else
pstatus blue NO
fi
else
pstatus blue NO
fi
fi
elif [ "$sys_interface_available" = 0 ]; then
# we have no sysfs but were asked to use it only!
msg="/sys vulnerability interface use forced, but it's not available!"
status=UNK
fi
# Test if the current host is a Xen PV Dom0 / DomU
if [ -d "/proc/xen" ]; then
# XXX do we have a better way that relying on dmesg?
dmesg_grep 'Booting paravirtualized kernel on Xen$'; ret=$?
if [ $ret -eq 2 ]; then
_warn "dmesg truncated, Xen detection will be unreliable. Please reboot and relaunch this script"
elif [ $ret -eq 0 ]; then
if [ -e /proc/xen/capabilities ] && grep -q "control_d" /proc/xen/capabilities; then
xen_pv_domo=1
else
xen_pv_domu=1
fi
fi
fi
if [ "$opt_live" = 1 ]; then
# checking whether we're running under Xen PV 64 bits. If yes, we are affected by variant3
# (unless we are a Dom0)
_info_nol "* Running as a Xen PV DomU: "
if [ "$xen_pv_domu" = 1 ]; then
pstatus red YES
else
pstatus green NO
fi
fi
cve='CVE-2017-5754'
if ! is_cpu_vulnerable 3; then
# override status & msg in case CPU is not vulnerable after all
@ -1490,8 +1498,10 @@ check_variant3()
if [ "$opt_live" = 1 ]; then
if [ "$kpti_enabled" = 1 ]; then
pvulnstatus $cve OK "PTI mitigates the vulnerability"
elif [ "$xen_pv" = 1 ]; then
pvulnstatus $cve OK "Xen PV 64 bits is not vulnerable"
elif [ "$xen_pv_domo" = 1 ]; then
pvulnstatus $cve OK "Xen Dom0s are safe and do not require PTI"
elif [ "$xen_pv_domu" = 1 ]; then
pvulnstatus $cve VULN "Xen PV DomUs are vulnerable and need to be run in HVM, PVHVM or PVH mode"
else
pvulnstatus $cve VULN "PTI is needed to mitigate the vulnerability"
fi
@ -1505,9 +1515,26 @@ check_variant3()
fi
fi
else
[ "$msg" = "Vulnerable" ] && msg="PTI is needed to mitigate the vulnerability"
if [ "$xen_pv_domo" = 1 ]; then
msg="Xen Dom0s are safe and do not require PTI"
status="OK"
elif [ "$xen_pv_domu" = 1 ]; then
msg="Xen PV DomUs are vulnerable and need to be run in HVM, PVHVM or PVH mode"
status="VULN"
elif [ "$msg" = "Vulnerable" ]; then
msg="PTI is needed to mitigate the vulnerability"
fi
pvulnstatus $cve "$status" "$msg"
fi
# Warn the user about XSA-254 recommended mitigations
if [ "$xen_pv_domo" = 1 ]; then
_warn
_warn "This host is a Xen Dom0. Please make sure that you are running your DomUs"
_warn "in HVM, PVHVM or PVH mode to prevent any guest-to-host / host-to-guest attacks."
_warn
_warn "See https://blog.xenproject.org/2018/01/22/xen-project-spectre-meltdown-faq-jan-22-update/ and XSA-254 for details."
fi
}
check_cpu