Add the 'fs.protected_symlinks' check

kernel_hardening_checker/checks.py

@@ -580,7 +580,6 @@ def normalize_cmdline_options(option, value):
 # TODO: draft of security hardening sysctls:
 #    what about bpf_jit_enable?
 #    vm.mmap_min_addr has a good value
-#    fs.protected_symlinks=1
 #    fs.protected_hardlinks=1
 #    fs.protected_fifos=2
 #    fs.protected_regular=2
@@ -615,3 +614,5 @@ def add_sysctl_checks(l, arch):
     l += [SysctlCheck('cut_attack_surface', 'kspp', 'vm.unprivileged_userfaultfd', '0')]
           # At first, it disabled unprivileged userfaultfd,
           # and since v5.11 it enables unprivileged userfaultfd for user-mode only.
+
+    l += [SysctlCheck('harden_userspace', 'kspp', 'fs.protected_symlinks', '1')]