bump to v0.25 to reflect changes

Produce JSON output formatted for Puppet, Ansible, Chef...

README.md

@@ -1,13 +1,17 @@
 Spectre & Meltdown Checker
 ==========================
 
-A simple shell script to tell if your Linux installation is vulnerable against the 3 "speculative execution" CVEs.
+A simple shell script to tell if your Linux installation is vulnerable against the 3 "speculative execution" CVEs that were made public early 2018.
 
 Without options, it'll inspect you currently running kernel. 
 You can also specify a kernel image on the command line, if you'd like to inspect a kernel you're not running.
 
 The script will do its best to detect mitigations, including backported non-vanilla patches, regardless of the advertised kernel version number.
 
+## Example of script output
+
+![checker](https://framapic.org/6O4v4AAwMenv/M6J4CFWwsB3z.png)
+
 ## Quick summary of the CVEs
 
 **CVE-2017-5753** bounds check bypass (Spectre Variant 1)
@@ -29,68 +33,13 @@ The script will do its best to detect mitigations, including backported non-vani
    - Mitigation: updated kernel (with PTI/KPTI patches), updating the kernel is enough
    - Performance impact of the mitigation: low to medium
 
-## Example of script output
+## Disclaimer
 
-### Ubuntu LTS (before official patches)
+This tool does its best to determine whether your system is immune (or has proper mitigations in place) for the collectively named "speculative execution" vulnerabilities. It doesn't attempt to run any kind of exploit, and can't guarantee that your system is secure, but rather helps you verifying whether your system has the known correct mitigations in place.
+However, some mitigations could also exist in your kernel that this script doesn't know (yet) how to detect, or it might falsely detect mitigations that in the end don't work as expected (for example, on backported or modified kernels).
 
-```
+Your system exposure also depends on your CPU. As of now, AMD and ARM processors are marked as immune to some or all of these vulnerabilities (except some specific ARM models). All Intel processors manufactured since circa 1995 are thought to be vulnerable. Whatever processor one uses, one might seek more information from the manufacturer of that processor and/or of the device in which it runs.
-$ sudo ./spectre-and-meltdown.sh
-Spectre and Meltdown mitigation detection tool v0.16
 
-Checking for vulnerabilities against live running kernel Linux 4.4.0-104-generic #127-Ubuntu SMP Mon Dec 11 12:16:42 UTC 2017 x86_64
+The nature of the discovered vulnerabilities being quite new, the landscape of vulnerable processors can be expected to change over time, which is why this script makes the assumption that all CPUs are vulnerable, except if the manufacturer explicitely stated otherwise in a verifiable public announcement.
-Will use vmlinux image /boot/vmlinuz-4.4.0-104-generic
-Will use kconfig /boot/config-4.4.0-104-generic
-Will use System.map file /boot/System.map-4.4.0-104-generic
 
-CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
+This tool has been released in the hope that it'll be useful, but don't use it to jump to conclusions about your security.
-* Kernel compiled with LFENCE opcode inserted at the proper places:  NO  (only 38 opcodes found, should be >= 70)
-> STATUS:  VULNERABLE 
-
-CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
-* Mitigation 1
-*   Hardware (CPU microcode) support for mitigation:  NO 
-*   Kernel support for IBRS:  NO 
-*   IBRS enabled for Kernel space:  NO 
-*   IBRS enabled for User space:  NO 
-* Mitigation 2
-*   Kernel compiled with retpoline option:  NO 
-*   Kernel compiled with a retpoline-aware compiler:  NO 
-> STATUS:  VULNERABLE  (IBRS hardware + kernel support OR kernel with retpoline are needed to mitigate the vulnerability)
-
-CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
-* Kernel supports Page Table Isolation (PTI):  NO 
-* PTI enabled and active:  NO 
-> STATUS:  VULNERABLE  (PTI is needed to mitigate the vulnerability)
-```
-
-### First patched kernel of RHEL6
-
-```
-$ sudo ./spectre-meltdown-checker.sh --kernel /tmp/vmlinuz-2.6.32-696.18.7.el6.x86_64 --config /tmp/config-2.6.32-696.18.7.el6.x86_64 --map /tmp/System.map-2.6.32-696.18.7.el6.x86_64
-Spectre and Meltdown mitigation detection tool v0.16
-
-Checking for vulnerabilities against specified kernel
-Will use vmlinux image /tmp/vmlinuz-2.6.32-696.18.7.el6.x86_64
-Will use kconfig /tmp/config-2.6.32-696.18.7.el6.x86_64
-Will use System.map file /tmp/System.map-2.6.32-696.18.7.el6.x86_64
-
-CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
-* Kernel compiled with LFENCE opcode inserted at the proper places:  YES  (84 opcodes found, which is >= 70)
-> STATUS:  NOT VULNERABLE 
-
-CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
-* Mitigation 1
-*   Hardware (CPU microcode) support for mitigation:  NO 
-*   Kernel support for IBRS:  YES 
-*   IBRS enabled for Kernel space:  N/A  (not testable in offline mode)
-*   IBRS enabled for User space:  N/A  (not testable in offline mode)
-* Mitigation 2
-*   Kernel compiled with retpoline option:  NO 
-*   Kernel compiled with a retpoline-aware compiler:  NO 
-> STATUS:  NOT VULNERABLE  (offline mode: IBRS will mitigate the vulnerability if enabled at runtime)
-
-CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
-* Kernel supports Page Table Isolation (PTI):  YES 
-* PTI enabled and active:  N/A  (can't verify if PTI is enabled in offline mode)
-> STATUS:  NOT VULNERABLE  (offline mode: PTI will mitigate the vulnerability if enabled at runtime)
-```

spectre-meltdown-checker.sh

@@ -8,7 +8,7 @@
 #
 # Stephane Lesimple
 #
-VERSION=0.21
+VERSION=0.25
 
 # Script configuration
 show_usage()
@@ -34,7 +34,11 @@ show_usage()
 	Options:
 		--no-color			Don't use color codes
 		-v, --verbose			Increase verbosity level
-		--batch				Produce machine readable output
+		--batch text			Produce machine readable output, this is the default if --batch is specified alone
+		--batch json			Produce JSON output formatted for Puppet, Ansible, Chef...
+		--batch nrpe			Produce machine readable output formatted for NRPE
+		--variant [1,2,3]		Specify which variant you'd like to check, by default all variants are checked
+						Can be specified multiple times (e.g. --variant 2 --variant 3)
 
 	IMPORTANT:
 	A false sense of security is worse than no security at all.
@@ -76,7 +80,16 @@ opt_live_explicit=0
 opt_live=1
 opt_no_color=0
 opt_batch=0
+opt_batch_format="text"
 opt_verbose=1
+opt_variant1=0
+opt_variant2=0
+opt_variant3=0
+opt_allvariants=1
+
+nrpe_critical=0
+nrpe_unknown=0
+nrpe_vuln=""
 
 __echo()
 {
@@ -127,6 +140,11 @@ _verbose()
 	_echo 2 "$@"
 }
 
+_debug()
+{
+	_echo 3 "(debug) $@"
+}
+
 is_cpu_vulnerable()
 {
 	# param: 1, 2 or 3 (variant)
@@ -201,7 +219,7 @@ parse_opt_file()
 		show_header
 		echo "$0: error: $option_value is not a file" >&2
 		exit 1
-	elif [ ! -e "$option_value" ]; then
+	elif [ ! -r "$option_value" ]; then
 		show_header
 		echo "$0: error: couldn't read $option_value (are you root?)" >&2
 		exit 1
@@ -236,9 +254,33 @@ while [ -n "$1" ]; do
 		opt_batch=1
 		opt_verbose=0
 		shift
+		case "$1" in
+			text|nrpe|json) opt_batch_format="$1"; shift;;
+			--*) ;;    # allow subsequent flags
+			'') ;;     # allow nothing at all
+			*)
+				echo "$0: error: unknown batch format '$1'"
+				echo "$0: error: --batch expects a format from: text, nrpe, json"
+				exit 1 >&2
+				;;
+		esac
 	elif [ "$1" = "-v" -o "$1" = "--verbose" ]; then
 		opt_verbose=$(expr $opt_verbose + 1)
 		shift
+	elif [ "$1" = "--variant" ]; then
+		if [ -z "$2" ]; then
+			echo "$0: error: option --variant expects a parameter (1, 2 or 3)" >&2
+			exit 1
+		fi
+		case "$2" in
+			1) opt_variant1=1; opt_allvariants=0;;
+			2) opt_variant2=1; opt_allvariants=0;;
+			3) opt_variant3=1; opt_allvariants=0;;
+			*)
+				echo "$0: error: invalid parameter '$2' for --variant, expected either 1, 2 or 3" >&2;
+				exit 1;;
+		esac
+		shift 2
 	elif [ "$1" = "-h" -o "$1" = "--help" ]; then
 		show_header
 		show_usage
@@ -280,7 +322,31 @@ pstatus()
 # Arguments are: CVE UNK/OK/VULN description
 pvulnstatus()
 {
-	[ "$opt_batch" = 1 ] && _echo 0 "$1: $2 ($3)"
+	if [ "$opt_batch" = 1 ]; then
+                case "$opt_batch_format" in
+                        text) _echo 0 "$1: $2 ($3)";;
+                        nrpe)
+                              case "$2" in
+                                       UKN) nrpe_unknown="1";;
+                                       VULN) nrpe_critical="1"; nrpe_vuln="$nrpe_vuln $1";;
+                              esac
+                              ;;
+                        json)
+                              case "$1" in
+                                       CVE-2017-5753) aka="SPECTRE VARIANT 1";;
+                                       CVE-2017-5715) aka="SPECTRE VARIANT 2";;
+                                       CVE-2017-5754) aka="MELTDOWN";;
+                              esac
+                              case "$2" in
+                                       UKN)  is_vuln="unknown";;
+                                       VULN) is_vuln="true";;
+                                       OK)   is_vuln="false";;
+                              esac
+                              json_output="${json_output:-[}{\"NAME\":\""$aka"\",\"CVE\":\""$1"\",\"VULNERABLE\":$is_vuln,\"INFOS\":\""$3"\"},"
+                              ;;
+		esac
+	fi
+
 	_info_nol "> \033[46m\033[30mSTATUS:\033[0m "
 	vulnstatus="$2"
 	shift 2
@@ -312,7 +378,7 @@ vmlinux=''
 vmlinux_err=''
 check_vmlinux()
 {
-	readelf -h $1 > /dev/null 2>&1 || return 1
+	readelf -h "$1" > /dev/null 2>&1 || return 1
 	return 0
 }
 
@@ -322,15 +388,22 @@ try_decompress()
 	# "grep" that report the byte offset of the line instead of the pattern.
 
 	# Try to find the header ($1) and decompress from here
-	for     pos in `tr "$1\n$2" "\n$2=" < "$5" | grep -abo "^$2"`
+	for     pos in `tr "$1\n$2" "\n$2=" < "$6" | grep -abo "^$2"`
 	do
-		if ! which $3 >/dev/null 2>&1; then
+		_debug "try_decompress: magic for $3 found at offset $pos"
-			vmlinux_err="missing '$3' tool, please install it, usually it's in the '$4' package"
+		if ! which "$3" >/dev/null 2>&1; then
+			vmlinux_err="missing '$3' tool, please install it, usually it's in the '$5' package"
 			return 0
 		fi
 		pos=${pos%%:*}
-		tail -c+$pos "$5" | $3 > $vmlinuxtmp 2> /dev/null
+		tail -c+$pos "$6" 2>/dev/null | $3 $4 > $vmlinuxtmp 2>/dev/null
-		check_vmlinux "$vmlinuxtmp" && vmlinux=$vmlinuxtmp && return 0
+		if check_vmlinux "$vmlinuxtmp"; then
+			vmlinux="$vmlinuxtmp"
+			_debug "try_decompress: decompressed with $3 successfully!"
+			return 0
+		else
+			_debug "try_decompress: decompression with $3 did not work"
+		fi
 	done
 	return 1
 }
@@ -350,11 +423,12 @@ extract_vmlinux()
 	fi
 
 	# That didn't work, so retry after decompression.
-	try_decompress '\037\213\010' xy    gunzip     gunzip	"$1" && return 0
+	try_decompress '\037\213\010'     xy    gunzip  ''      gunzip      "$1" && return 0
-	try_decompress '\3757zXZ\000' abcde unxz       xz-utils	"$1" && return 0
+	try_decompress '\3757zXZ\000'     abcde unxz    ''      xz-utils    "$1" && return 0
-	try_decompress 'BZh'          xy    bunzip2    bzip2	"$1" && return 0
+	try_decompress 'BZh'              xy    bunzip2 ''      bzip2       "$1" && return 0
-	try_decompress '\135\0\0\0'   xxx   unlzma     xz-utils	"$1" && return 0
+	try_decompress '\135\0\0\0'       xxx   unlzma  ''      xz-utils    "$1" && return 0
-	try_decompress '\211\114\132' xy    'lzop -d'  lzop	"$1" && return 0
+	try_decompress '\211\114\132'     xy    'lzop'  '-d'    lzop        "$1" && return 0
+	try_decompress '\002\041\114\030' xyy   'lz4'   '-d -l' liblz4-tool "$1" && return 0
 	return 1
 }
 
@@ -381,12 +455,25 @@ if [ "$opt_live" = 1 ]; then
 	_info "Checking for vulnerabilities against live running kernel \033[35m"$(uname -s) $(uname -r) $(uname -v) $(uname -m)"\033[0m"
 
 	# try to find the image of the current running kernel
+	# first, look for the BOOT_IMAGE hint in the kernel cmdline
+	if [ -r /proc/cmdline ] && grep -q 'BOOT_IMAGE=' /proc/cmdline; then
+		opt_kernel=$(grep -Eo 'BOOT_IMAGE=[^ ]+' /proc/cmdline | cut -d= -f2)
+		_debug "found opt_kernel=$opt_kernel in /proc/cmdline"
+		# if we have a dedicated /boot partition, our bootloader might have just called it /
+		# so try to prepend /boot and see if we find anything
+		[ -e "/boot/$opt_kernel" ] && opt_kernel="/boot/$opt_kernel"
+		_debug "opt_kernel is now $opt_kernel"
+		# else, the full path is already there (most probably /boot/something)
+	fi
+	# if we didn't find a kernel, default to guessing
+	if [ ! -e "$opt_kernel" ]; then
 		[ -e /boot/vmlinuz-linux       ] && opt_kernel=/boot/vmlinuz-linux
 		[ -e /boot/vmlinuz-linux-libre ] && opt_kernel=/boot/vmlinuz-linux-libre
 		[ -e /boot/vmlinuz-$(uname -r) ] && opt_kernel=/boot/vmlinuz-$(uname -r)
 		[ -e /boot/kernel-$( uname -r) ] && opt_kernel=/boot/kernel-$( uname -r)
 		[ -e /boot/bzImage-$(uname -r) ] && opt_kernel=/boot/bzImage-$(uname -r)
 		[ -e /boot/kernel-genkernel-$(uname -m)-$(uname -r) ] && opt_kernel=/boot/kernel-genkernel-$(uname -m)-$(uname -r)
+	fi
 
 	# system.map
 	if [ -e /proc/kallsyms ] ; then
@@ -440,15 +527,38 @@ fi
 
 _info
 
-###########
+# end of header stuff
-# SPECTRE 1
-_info "\033[1;34mCVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'\033[0m"
-_info_nol "* Checking count of LFENCE opcodes in kernel: "
 
-status=0
+# now we define some util functions and the check_*() funcs, as
-if [ -n "$vmlinux_err" ]; then
+# the user can choose to execute only some of those
+
+mount_debugfs()
+{
+	if [ ! -e /sys/kernel/debug/sched_features ]; then
+		# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
+		mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
+	fi
+}
+
+umount_debugfs()
+{
+	if [ "$mounted_debugfs" = 1 ]; then
+		# umount debugfs if we did mount it ourselves
+		umount /sys/kernel/debug
+	fi
+}
+
+###################
+# SPECTRE VARIANT 1
+check_variant1()
+{
+	_info "\033[1;34mCVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'\033[0m"
+	_info_nol "* Checking count of LFENCE opcodes in kernel: "
+
+	status=0
+	if [ -n "$vmlinux_err" ]; then
 		pstatus yellow UNKNOWN "$vmlinux_err"
-else
+	else
 		if ! which objdump >/dev/null 2>&1; then
 			pstatus yellow UNKNOWN "missing 'objdump' tool, please install it, usually it's in the binutils package"
 		else
@@ -467,31 +577,33 @@ else
 				status=2
 			fi
 		fi
-fi
+	fi
 
-if ! is_cpu_vulnerable 1; then
+	if ! is_cpu_vulnerable 1; then
 		pvulnstatus CVE-2017-5753 OK "your CPU vendor reported your CPU model as not vulnerable"
-else
+	else
 		case "$status" in
 			0) pvulnstatus CVE-2017-5753 UNK "impossible to check ${vmlinux}";;
 			1) pvulnstatus CVE-2017-5753 VULN 'heuristic to be improved when official patches become available';;
 			2) pvulnstatus CVE-2017-5753 OK 'heuristic to be improved when official patches become available';;
 		esac
-fi
+	fi
+}
 
-###########
+###################
-# VARIANT 2
+# SPECTRE VARIANT 2
-_info
+check_variant2()
-_info "\033[1;34mCVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'\033[0m"
+{
-_info "* Mitigation 1"
+	_info "\033[1;34mCVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'\033[0m"
-_info_nol "*   Hardware (CPU microcode) support for mitigation: "
+	_info "* Mitigation 1"
-if [ ! -e /dev/cpu/0/msr ]; then
+	_info_nol "*   Hardware (CPU microcode) support for mitigation: "
+	if [ ! -e /dev/cpu/0/msr ]; then
 		# try to load the module ourselves (and remember it so we can rmmod it afterwards)
 		modprobe msr 2>/dev/null && insmod_msr=1
-fi
+	fi
-if [ ! -e /dev/cpu/0/msr ]; then
+	if [ ! -e /dev/cpu/0/msr ]; then
 		pstatus yellow UNKNOWN "couldn't read /dev/cpu/0/msr, is msr support enabled in your kernel?"
-else
+	else
 		# the new MSR 'SPEC_CTRL' is at offset 0x48
 		# here we use dd, it's the same as using 'rdmsr 0x48' but without needing the rdmsr tool
 		# if we get a read error, the MSR is not there
@@ -501,43 +613,44 @@ else
 		else
 			pstatus red NO
 		fi
-fi
+	fi
 
-if [ "$insmod_msr" = 1 ]; then
+	if [ "$insmod_msr" = 1 ]; then
 		# if we used modprobe ourselves, rmmod the module
 		rmmod msr 2>/dev/null
-fi
+	fi
 
-_info_nol "*   Kernel support for IBRS: "
+	_info_nol "*   Kernel support for IBRS: "
-if [ "$opt_live" = 1 ]; then
+	if [ "$opt_live" = 1 ]; then
-	if [ ! -e /sys/kernel/debug/sched_features ]; then
+		mount_debugfs
-		# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
+		for ibrs_file in \
-		mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
+			/sys/kernel/debug/ibrs_enabled \
-	fi
+			/sys/kernel/debug/x86/ibrs_enabled \
-	if [ -e /sys/kernel/debug/ibrs_enabled ]; then
+			/proc/sys/kernel/ibrs_enabled; do
+			if [ -e "$ibrs_file" ]; then
 				# if the file is there, we have IBRS compiled-in
+				# /sys/kernel/debug/ibrs_enabled: vanilla
+				# /sys/kernel/debug/x86/ibrs_enabled: RedHat (see https://access.redhat.com/articles/3311301)
+				# /proc/sys/kernel/ibrs_enabled: OpenSUSE tumbleweed
 				pstatus green YES
 				ibrs_supported=1
-		ibrs_enabled=$(cat /sys/kernel/debug/ibrs_enabled 2>/dev/null)
+				ibrs_enabled=$(cat "$ibrs_file" 2>/dev/null)
-	elif [ -e /sys/kernel/debug/x86/ibrs_enabled ]; then
+				break
-		# RedHat uses a different path (see https://access.redhat.com/articles/3311301)
-		pstatus green YES
-		ibrs_supported=1
-		ibrs_enabled=$(cat /sys/kernel/debug/x86/ibrs_enabled 2>/dev/null)
 			fi
-fi
+		done
-if [ "$ibrs_supported" != 1 -a -n "$opt_map" ]; then
+	fi
+	if [ "$ibrs_supported" != 1 -a -n "$opt_map" ]; then
 		if grep -q spec_ctrl "$opt_map"; then
 			pstatus green YES
 			ibrs_supported=1
 		fi
-fi
+	fi
-if [ "$ibrs_supported" != 1 ]; then
+	if [ "$ibrs_supported" != 1 ]; then
 		pstatus red NO
-fi
+	fi
 
-_info_nol "*   IBRS enabled for Kernel space: "
+	_info_nol "*   IBRS enabled for Kernel space: "
-if [ "$opt_live" = 1 ]; then
+	if [ "$opt_live" = 1 ]; then
 		# 0 means disabled
 		# 1 is enabled only for kernel space
 		# 2 is enabled for kernel and user space
@@ -547,43 +660,43 @@ if [ "$opt_live" = 1 ]; then
 			1 | 2) pstatus green YES;;
 			*)     pstatus yellow UNKNOWN;;
 		esac
-else
+	else
 		pstatus blue N/A "not testable in offline mode"
-fi
+	fi
 
-_info_nol "*   IBRS enabled for User space: "
+	_info_nol "*   IBRS enabled for User space: "
-if [ "$opt_live" = 1 ]; then
+	if [ "$opt_live" = 1 ]; then
 		case "$ibrs_enabled" in
 			"") [ "$ibrs_supported" = 1 ] && pstatus yellow UNKNOWN || pstatus red NO;;
 			0 | 1) pstatus red NO;;
 			2) pstatus green YES;;
 			*) pstatus yellow UNKNOWN;;
 		esac
-else
+	else
 		pstatus blue N/A "not testable in offline mode"
-fi
+	fi
 
-_info "* Mitigation 2"
+	_info "* Mitigation 2"
-_info_nol "*   Kernel compiled with retpoline option: "
+	_info_nol "*   Kernel compiled with retpoline option: "
-# We check the RETPOLINE kernel options
+	# We check the RETPOLINE kernel options
-if [ -r "$opt_config" ]; then
+	if [ -r "$opt_config" ]; then
 		if grep -q '^CONFIG_RETPOLINE=y' "$opt_config"; then
 			pstatus green YES
 			retpoline=1
 		else
 			pstatus red NO
 		fi
-else
+	else
 		pstatus yellow UNKNOWN "couldn't read your kernel configuration"
-fi
+	fi
 
-_info_nol "*   Kernel compiled with a retpoline-aware compiler: "
+	_info_nol "*   Kernel compiled with a retpoline-aware compiler: "
-# Now check if the compiler used to compile the kernel knows how to insert retpolines in generated asm
+	# Now check if the compiler used to compile the kernel knows how to insert retpolines in generated asm
-# For gcc, this is -mindirect-branch=thunk-extern (detected by the kernel makefiles)
+	# For gcc, this is -mindirect-branch=thunk-extern (detected by the kernel makefiles)
-# See gcc commit https://github.com/hjl-tools/gcc/commit/23b517d4a67c02d3ef80b6109218f2aadad7bd79
+	# See gcc commit https://github.com/hjl-tools/gcc/commit/23b517d4a67c02d3ef80b6109218f2aadad7bd79
-# In latest retpoline LKML patches, the noretpoline_setup symbol exists only if CONFIG_RETPOLINE is set
+	# In latest retpoline LKML patches, the noretpoline_setup symbol exists only if CONFIG_RETPOLINE is set
-# *AND* if the compiler is retpoline-compliant, so look for that symbol
+	# *AND* if the compiler is retpoline-compliant, so look for that symbol
-if [ -n "$opt_map" ]; then
+	if [ -n "$opt_map" ]; then
 		# look for the symbol
 		if grep -qw noretpoline_setup "$opt_map"; then
 			retpoline_compiler=1
@@ -591,7 +704,7 @@ if [ -n "$opt_map" ]; then
 		else
 			pstatus red NO
 		fi
-elif [ -n "$vmlinux" ]; then
+	elif [ -n "$vmlinux" ]; then
 		# look for the symbol
 		if which nm >/dev/null 2>&1; then
 			# the proper way: use nm and look for the symbol
@@ -609,50 +722,52 @@ elif [ -n "$vmlinux" ]; then
 		else
 			pstatus red NO
 		fi
-else
+	else
 		pstatus yellow UNKNOWN "couldn't find your kernel image or System.map"
-fi
+	fi
 
-if ! is_cpu_vulnerable 2; then
+	if ! is_cpu_vulnerable 2; then
 		pvulnstatus CVE-2017-5715 OK "your CPU vendor reported your CPU model as not vulnerable"
-elif [ "$retpoline" = 1 -a "$retpoline_compiler" = 1 ]; then
+	elif [ "$retpoline" = 1 -a "$retpoline_compiler" = 1 ]; then
 		pvulnstatus CVE-2017-5715 OK "retpoline mitigate the vulnerability"
-elif [ "$opt_live" = 1 ]; then
+	elif [ "$opt_live" = 1 ]; then
 		if [ "$ibrs_enabled" = 1 -o "$ibrs_enabled" = 2 ]; then
 			pvulnstatus CVE-2017-5715 OK "IBRS mitigates the vulnerability"
 		else
 			pvulnstatus CVE-2017-5715 VULN "IBRS hardware + kernel support OR kernel with retpoline are needed to mitigate the vulnerability"
 		fi
-else
+	else
 		if [ "$ibrs_supported" = 1 ]; then
 			pvulnstatus CVE-2017-5715 OK "offline mode: IBRS will mitigate the vulnerability if enabled at runtime"
 		else
 			pvulnstatus CVE-2017-5715 VULN "IBRS hardware + kernel support OR kernel with retpoline are needed to mitigate the vulnerability"
 		fi
-fi
+	fi
+}
 
-##########
+########################
-# MELTDOWN
+# MELTDOWN aka VARIANT 3
-_info
+check_variant3()
-_info "\033[1;34mCVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'\033[0m"
+{
-_info_nol "* Kernel supports Page Table Isolation (PTI): "
+	_info "\033[1;34mCVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'\033[0m"
-kpti_support=0
+	_info_nol "* Kernel supports Page Table Isolation (PTI): "
-kpti_can_tell=0
+	kpti_support=0
-if [ -n "$opt_config" ]; then
+	kpti_can_tell=0
+	if [ -n "$opt_config" ]; then
 		kpti_can_tell=1
 		if grep -Eq '^(CONFIG_PAGE_TABLE_ISOLATION|CONFIG_KAISER)=y' "$opt_config"; then
 			kpti_support=1
 		fi
-fi
+	fi
-if [ "$kpti_support" = 0 -a -n "$opt_map" ]; then
+	if [ "$kpti_support" = 0 -a -n "$opt_map" ]; then
 		# it's not an elif: some backports don't have the PTI config but still include the patch
 		# so we try to find an exported symbol that is part of the PTI patch in System.map
 		kpti_can_tell=1
 		if grep -qw kpti_force_enabled "$opt_map"; then
 			kpti_support=1
 		fi
-fi
+	fi
-if [ "$kpti_support" = 0 -a -n "$vmlinux" ]; then
+	if [ "$kpti_support" = 0 -a -n "$vmlinux" ]; then
 		# same as above but in case we don't have System.map and only vmlinux, look for the
 		# nopti option that is part of the patch (kernel command line option)
 		kpti_can_tell=1
@@ -663,18 +778,19 @@ if [ "$kpti_support" = 0 -a -n "$vmlinux" ]; then
 				kpti_support=1
 			fi
 		fi
-fi
+	fi
 
-if [ "$kpti_support" = 1 ]; then
+	if [ "$kpti_support" = 1 ]; then
 		pstatus green YES
-elif [ "$kpti_can_tell" = 1 ]; then
+	elif [ "$kpti_can_tell" = 1 ]; then
 		pstatus red NO
-else
+	else
 		pstatus yellow UNKNOWN "couldn't read your kernel configuration nor System.map file"
-fi
+	fi
 
-_info_nol "* PTI enabled and active: "
+	mount_debugfs
-if [ "$opt_live" = 1 ]; then
+	_info_nol "* PTI enabled and active: "
+	if [ "$opt_live" = 1 ]; then
 		if grep ^flags /proc/cpuinfo | grep -qw pti; then
 			# vanilla PTI patch sets the 'pti' flag in cpuinfo
 			kpti_enabled=1
@@ -685,7 +801,10 @@ if [ "$opt_live" = 1 ]; then
 			# RedHat Backport creates a dedicated file, see https://access.redhat.com/articles/3311301
 			kpti_enabled=$(cat /sys/kernel/debug/x86/pti_enabled 2>/dev/null)
 		elif dmesg | grep -Eq 'Kernel/User page tables isolation: enabled|Kernel page table isolation enabled'; then
-		# if we can't find the flag, grep in dmesg
+			# if we can't find the flag, grep dmesg output
+			kpti_enabled=1
+		elif [ -r /var/log/dmesg ] && grep -Eq 'Kernel/User page tables isolation: enabled|Kernel page table isolation enabled' /var/log/dmesg; then
+			# if we can't find the flag in dmesg output, grep in /var/log/dmesg when readable
 			kpti_enabled=1
 		else
 			kpti_enabled=0
@@ -695,33 +814,60 @@ if [ "$opt_live" = 1 ]; then
 		else
 			pstatus red NO
 		fi
-else
+	else
 		pstatus blue N/A "can't verify if PTI is enabled in offline mode"
-fi
+	fi
 
-if [ "$mounted_debugfs" = 1 ]; then
+	if ! is_cpu_vulnerable 3; then
-	# umount debugfs if we did mount it ourselves
-	umount /sys/kernel/debug
-fi
-
-if ! is_cpu_vulnerable 3; then
 		pvulnstatus CVE-2017-5754 OK "your CPU vendor reported your CPU model as not vulnerable"
-elif [ "$opt_live" = 1 ]; then
+	elif [ "$opt_live" = 1 ]; then
 		if [ "$kpti_enabled" = 1 ]; then
 			pvulnstatus CVE-2017-5754 OK "PTI mitigates the vulnerability"
 		else
 			pvulnstatus CVE-2017-5754 VULN "PTI is needed to mitigate the vulnerability"
 		fi
-else
+	else
 		if [ "$kpti_support" = 1 ]; then
 			pvulnstatus CVE-2017-5754 OK "offline mode: PTI will mitigate the vulnerability if enabled at runtime"
 		else
 			pvulnstatus CVE-2017-5754 VULN "PTI is needed to mitigate the vulnerability"
 		fi
+	fi
+}
+
+# now run the checks the user asked for
+if [ "$opt_variant1" = 1 -o "$opt_allvariants" = 1 ]; then
+	check_variant1
+	_info
+fi
+if [ "$opt_variant2" = 1 -o "$opt_allvariants" = 1 ]; then
+	check_variant2
+	_info
+fi
+if [ "$opt_variant3" = 1 -o "$opt_allvariants" = 1 ]; then
+	check_variant3
+	_info
 fi
 
-_info
+_info "A false sense of security is worse than no security at all, see --disclaimer"
 
-_info "A false sense of security is worst than no security at all, see --disclaimer"
+# this'll umount only if we mounted debugfs ourselves
+umount_debugfs
 
+# cleanup the temp decompressed config
 [ -n "$dumped_config" ] && rm -f "$dumped_config"
+
+if [ "$opt_batch" = 1 -a "$opt_batch_format" = "nrpe" ]; then
+	if [ ! -z "$nrpe_vuln" ]; then
+		echo "Vulnerable:$nrpe_vuln"
+	else
+		echo "OK"
+	fi
+	[ "$nrpe_critical" = 1 ] && exit 2  # critical
+	[ "$nrpe_unknown" = 1 ] && exit 3  # unknown
+	exit 0  # ok
+fi
+
+if [ "$opt_batch" = 1 -a "$opt_batch_format" = "json" ]; then
+	_echo 0 ${json_output%?}]
+fi