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authorPaul Moore <paul@paul-moore.com>2023-03-17 12:43:07 -0400
committerPaul Moore <paul@paul-moore.com>2023-03-20 12:34:23 -0400
commitf22f9aaf6c3d92ebd5ad9e67acc03afebaaeb289 (patch)
treec47a7b91ce9f53aebcc8398582a5232d640b5c65 /security/loadpin
parenta7e4676e8e2cb158a4d24123de778087955e1b36 (diff)
selinux: remove the runtime disable functionality
After working with the larger SELinux-based distros for several years, we're finally at a place where we can disable the SELinux runtime disable functionality. The existing kernel deprecation notice explains the functionality and why we want to remove it: The selinuxfs "disable" node allows SELinux to be disabled at runtime prior to a policy being loaded into the kernel. If disabled via this mechanism, SELinux will remain disabled until the system is rebooted. The preferred method of disabling SELinux is via the "selinux=0" boot parameter, but the selinuxfs "disable" node was created to make it easier for systems with primitive bootloaders that did not allow for easy modification of the kernel command line. Unfortunately, allowing for SELinux to be disabled at runtime makes it difficult to secure the kernel's LSM hooks using the "__ro_after_init" feature. It is that last sentence, mentioning the '__ro_after_init' hardening, which is the real motivation for this change, and if you look at the diffstat you'll see that the impact of this patch reaches across all the different LSMs, helping prevent tampering at the LSM hook level. From a SELinux perspective, it is important to note that if you continue to disable SELinux via "/etc/selinux/config" it may appear that SELinux is disabled, but it is simply in an uninitialized state. If you load a policy with `load_policy -i`, you will see SELinux come alive just as if you had loaded the policy during early-boot. It is also worth noting that the "/sys/fs/selinux/disable" file is always writable now, regardless of the Kconfig settings, but writing to the file has no effect on the system, other than to display an error on the console if a non-zero/true value is written. Finally, in the several years where we have been working on deprecating this functionality, there has only been one instance of someone mentioning any user visible breakage. In this particular case it was an individual's kernel test system, and the workaround documented in the deprecation notice ("selinux=0" on the kernel command line) resolved the issue without problem. Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'security/loadpin')
-rw-r--r--security/loadpin/loadpin.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index d73a281adf86..b9d773f11232 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -214,7 +214,7 @@ static int loadpin_load_data(enum kernel_load_data_id id, bool contents)
return loadpin_check(NULL, (enum kernel_read_file_id) id);
}
-static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
+static struct security_hook_list loadpin_hooks[] __ro_after_init = {
LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),