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feat: add special extract_vmlinux mode for old RHEL kernels

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This commit is contained in:
Stéphane Lesimple 2018-03-24 23:58:13 +01:00
parent 37ce032888
commit 889172dbb1
1 changed files with 47 additions and 17 deletions
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64
spectre-meltdown-checker.sh
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@ -563,11 +563,32 @@ vmlinux=''
vmlinux_err=''
check_vmlinux()
{
_file="$1"
_desperate_mode="$2"
# checking the return code of readelf -h is not enough, we could get
# a damaged ELF file and validate it, check for stderr warnings too
_readelf_warnings=$("${opt_arch_prefix}readelf" -S "$1" 2>&1 >/dev/null); ret=$?
if [ $ret -eq 0 ] && [ -z "$_readelf_warnings" ]; then
return 0
_readelf_warnings=$("${opt_arch_prefix}readelf" -S "$_file" 2>&1 >/dev/null | tr "\n" "/"); ret=$?
_readelf_sections=$("${opt_arch_prefix}readelf" -S "$_file" 2>/dev/null | grep -c -e data -e text -e init)
_vmlinux_size=$(stat -c %s "$_file")
_debug "check_vmlinux: ret=$? size=$_vmlinux_size sections=$_readelf_sections warnings=$_readelf_warnings"
if [ -n "$_desperate_mode" ]; then
if "${opt_arch_prefix}strings" "$_file" | grep -Eq '^Linux version '; then
_debug "check_vmlinux (desperate): ... matched!"
return 0
else
_debug "check_vmlinux (desperate): ... invalid"
fi
else
if [ $ret -eq 0 ] && [ -z "$_readelf_warnings" ] && [ "$_readelf_sections" -gt 0 ]; then
if [ "$_vmlinux_size" -ge 100000 ]; then
_debug "check_vmlinux: ... file is valid"
return 0
else
_debug "check_vmlinux: ... file seems valid but is too small, ignoring"
fi
else
_debug "check_vmlinux: ... file is invalid"
fi
fi
return 1
}
@ -593,7 +614,7 @@ try_decompress()
# don't rely on $ret, sometimes it's != 0 but worked
# (e.g. gunzip ret=2 just means there was trailing garbage)
_debug "try_decompress: decompression with $3 failed (err=$ret)"
elif check_vmlinux "$vmlinuxtmp"; then
elif check_vmlinux "$vmlinuxtmp" "$7"; then
vmlinux="$vmlinuxtmp"
_debug "try_decompress: decompressed with $3 successfully!"
return 0
@ -623,13 +644,15 @@ extract_vmlinux()
fi
# That didn't work, so retry after decompression.
try_decompress '\037\213\010' xy gunzip '' gunzip "$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 '\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 '\002\041\114\030' xyy 'lz4' '-d -l' liblz4-tool "$1" && return 0
try_decompress '\177ELF' xxy 'cat' '' cat "$1" && return 0
for mode in '' 'desperate'; do
try_decompress '\037\213\010' xy gunzip '' gunzip "$1" "$mode" && return 0
try_decompress '\3757zXZ\000' abcde unxz '' xz-utils "$1" "$mode" && return 0
try_decompress 'BZh' xy bunzip2 '' bzip2 "$1" "$mode" && return 0
try_decompress '\135\0\0\0' xxx unlzma '' xz-utils "$1" "$mode" && return 0
try_decompress '\211\114\132' xy 'lzop' '-d' lzop "$1" "$mode" && return 0
try_decompress '\002\041\114\030' xyy 'lz4' '-d -l' liblz4-tool "$1" "$mode" && return 0
try_decompress '\177ELF' xxy 'cat' '' cat "$1" "$mode" && return 0
done
_verbose "Couldn't extract the kernel image, accuracy might be reduced"
return 1
}
@ -1399,12 +1422,17 @@ check_redhat_canonical_spectre()
redhat_canonical_spectre=-2
else
# Red Hat / Ubuntu specific variant1 patch is difficult to detect,
# let's use the same way than the official Red Hat detection script,
# and detect their specific variant2 patch. If it's present, it means
# that the variant1 patch is also present (both were merged at the same time)
# let's use the two same tricks than the official Red Hat detection script uses:
if "${opt_arch_prefix}strings" "$vmlinux" | grep -qw noibrs && "${opt_arch_prefix}strings" "$vmlinux" | grep -qw noibpb; then
# 1) detect their specific variant2 patch. If it's present, it means
# that the variant1 patch is also present (both were merged at the same time)
_debug "found redhat/canonical version of the variant2 patch (implies variant1)"
redhat_canonical_spectre=1
elif "${opt_arch_prefix}strings" "$vmlinux" | grep -q 'x86/pti:'; then
# 2) detect their specific variant3 patch. If it's present, but the variant2
# is not, it means that only variant1 is present in addition to variant3
_debug "found redhat/canonical version of the variant3 patch (implies variant1 but not variant2)"
redhat_canonical_spectre=2
else
redhat_canonical_spectre=0
fi
@ -1470,11 +1498,13 @@ check_variant1()
pstatus yellow UNKNOWN "couldn't check ($vmlinux_err)"
elif [ "$redhat_canonical_spectre" = 1 ]; then
pstatus green YES
elif [ "$redhat_canonical_spectre" = 2 ]; then
pstatus green YES "but without IBRS"
else
pstatus red NO
fi
if [ "$opt_verbose" -ge 2 ] || ( [ "$v1_mask_nospec" != 1 ] && [ "$redhat_canonical_spectre" != 1 ] ); then
if [ "$opt_verbose" -ge 2 ] || ( [ "$v1_mask_nospec" != 1 ] && [ "$redhat_canonical_spectre" != 1 ] && [ "$redhat_canonical_spectre" != 2 ] ); then
# this is a slow heuristic and we don't need it if we already know the kernel is patched
# but still show it in verbose mode
_info_nol "* Checking count of LFENCE instructions following a jump in kernel... "
@ -1491,7 +1521,7 @@ check_variant1()
# so let's push the threshold to 70.
# v0.33+: now only count lfence opcodes after a jump, way less error-prone
# non patched kernel have between 0 and 20 matches, patched ones have at least 40-45
nb_lfence=$("${opt_arch_prefix}objdump" -d "$vmlinux" | grep -w -B1 lfence | grep -Ewc 'jmp|jne|je')
nb_lfence=$("${opt_arch_prefix}objdump" -d "$vmlinux" 2>/dev/null | grep -w -B1 lfence | grep -Ewc 'jmp|jne|je')
if [ "$nb_lfence" -lt 30 ]; then
pstatus red NO "only $nb_lfence jump-then-lfence instructions found, should be >= 30 (heuristic)"
else
@ -1517,7 +1547,7 @@ check_variant1()
# if msg is empty, sysfs check didn't fill it, rely on our own test
if [ "$v1_mask_nospec" = 1 ]; then
pvulnstatus $cve OK "Kernel source has been patched to mitigate the vulnerability (array_index_mask_nospec)"
elif [ "$redhat_canonical_spectre" = 1 ]; then
elif [ "$redhat_canonical_spectre" = 1 ] || [ "$redhat_canonical_spectre" = 2 ]; then
pvulnstatus $cve OK "Kernel source has been patched to mitigate the vulnerability (Red Hat/Ubuntu patch)"
elif [ "$v1_lfence" = 1 ]; then
pvulnstatus $cve OK "Kernel source has PROBABLY been patched to mitigate the vulnerability (jump-then-lfence instructions heuristic)"