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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/bpf
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/bpf')
-rw-r--r--security/bpf/hooks.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c
index e5971fa74fd7..cfaf1d0e6a5f 100644
--- a/security/bpf/hooks.c
+++ b/security/bpf/hooks.c
@@ -6,7 +6,7 @@
#include <linux/lsm_hooks.h>
#include <linux/bpf_lsm.h>
-static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
+static struct security_hook_list bpf_lsm_hooks[] __ro_after_init = {
#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
LSM_HOOK_INIT(NAME, bpf_lsm_##NAME),
#include <linux/lsm_hook_defs.h>
@@ -22,7 +22,7 @@ static int __init bpf_lsm_init(void)
return 0;
}
-struct lsm_blob_sizes bpf_lsm_blob_sizes __lsm_ro_after_init = {
+struct lsm_blob_sizes bpf_lsm_blob_sizes __ro_after_init = {
.lbs_inode = sizeof(struct bpf_storage_blob),
.lbs_task = sizeof(struct bpf_storage_blob),
};