2018.7.25 追記
実行結果のサンプルについては、Fedora 確認方法 – 近代的CPUの脆弱性も併せてご参照ください。

確認方法

まず、Ubuntu の確認方法同様に dmesg と proc/cpuinfo を利用して確認してみます。

base on kernel - How to check that KPTI is enabled on my Ubuntu? - Ask Ubuntu

• /proc/cpuinfo
  grep -q "cpu_insecure|cpu_meltdown|kaiser" /proc/cpuinfo && echo "patched :)" || echo "unpatched :("
• dmesg
  dmesg | grep -q "Kernel/User page tables isolation: enabled" && echo "patched :)" || echo "unpatched :("

確認環境

Spec	Details
Product	Banana Pi M1 Classic
OS	Armbian 5.38
Soc	Allwinner A20 / Dual-Core ARM Cortex-A7 @ 1.0GHz
MEM	1GB

# cat /etc/issue
Debian GNU/Linux 9 \n \l

# cat /etc/debian_version 
9.4

# cat /proc/version 
Linux version 4.14.18-sunxi (root@xeon) (gcc version 7.2.1 20171011 (Linaro GCC 7.2-2017.11)) #24 SMP Fri Feb 9 16:24:32 CET 2018

実行サンプル

# dmesg | grep -q "Kernel/User page tables isolation: enabled" && echo "patched :)" || echo "unpatched :("
unpatched :(
# grep -q "cpu_insecure\|cpu_meltdown\|kaiser" /proc/cpuinfo && echo "patched :)" || echo "unpatched :("
unpatched :(
# ls -lh /sys/devices/system/cpu/vulnerabilities/
ls: '/sys/devices/system/cpu/vulnerabilities/' にアクセスできません: そのようなファイルやディレクトリはありません

先日の記事にも記載しましたが、OSが 32bit なので物の見事に全てNGになっています。

公式方法での確認

Debian 9 以降は、脆弱性の判断ツール Debian Package Tracker - spectre-meltdown-checker が使えます。

# sudo apt install -t stretch-backports spectre-meltdown-checker

以下のパッケージが新たにインストールされます:
  spectre-meltdown-checker

# sudo spectre-meltdown-checker
Spectre and Meltdown mitigation detection tool v0.37

Checking for vulnerabilities on current system
Kernel is Linux 4.14.18-sunxi #24 SMP Fri Feb 9 16:24:32 CET 2018 armv7l
CPU is ARM v7 model 0xc07

Hardware check
* CPU vulnerability to the three speculative execution attack variants
  * Vulnerable to Variant 1:  NO 
  * Vulnerable to Variant 2:  NO 
  * Vulnerable to Variant 3:  NO 

CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
* Kernel has array_index_mask_nospec (x86):  NO 
* Kernel has the Red Hat/Ubuntu patch:  NO 
* Kernel has mask_nospec64 (arm):  NO 
* Checking count of LFENCE instructions following a jump in kernel...  NO  (only 0 jump-then-lfence instructions found, should be >= 30 (heuristic))
> STATUS:  NOT VULNERABLE  (your CPU vendor reported your CPU model as not vulnerable)

CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
* Mitigation 1
  * Kernel is compiled with IBRS support:  NO 
    * IBRS enabled and active:  UNKNOWN 
  * Kernel is compiled with IBPB support:  NO 
    * IBPB enabled and active:  NO 
* Mitigation 2
  * Kernel has branch predictor hardening (arm):  NO 
  * Kernel compiled with retpoline option:  NO 
> STATUS:  NOT VULNERABLE  (your CPU vendor reported your CPU model as not vulnerable)

CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
* Kernel supports Page Table Isolation (PTI):  NO 
  * PTI enabled and active:  NO 
  * Reduced performance impact of PTI:  NO  (PCID/INVPCID not supported, performance impact of PTI will be significant)
* Running as a Xen PV DomU:  NO 
> STATUS:  NOT VULNERABLE  (your CPU vendor reported your CPU model as not vulnerable)

A false sense of security is worse than no security at all, see --disclaimer

上記、実行サンプルと同様に軒並みNGになっています。
当たり前ですね．．．。