selinux: treat atomic flags more carefully

The disabled/enforcing/initialized flags are all accessed concurrently
by threads so use the appropriate accessors that ensure atomicity and
document that it is expected.

Use smp_load/acquire...() helpers (with memory barriers) for the
initialized flag, since it gates access to the rest of the state
structures.

Note that the disabled flag is currently not used for anything other
than avoiding double disable, but it will be used for bailing out of
hooks once security_delete_hooks() is removed.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 11 insertions, 10 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 921283f47862..a81631f8cc5d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -272,7 +272,7 @@ static int __inode_security_revalidate(struct inode *inode,
 
 	might_sleep_if(may_sleep);
 
-	if (selinux_state.initialized &&
+	if (selinux_initialized(&selinux_state) &&
 	    isec->initialized != LABEL_INITIALIZED) {
 		if (!may_sleep)
 			return -ECHILD;
@@ -659,7 +659,7 @@ static int selinux_set_mnt_opts(struct super_block *sb,
 
 	mutex_lock(&sbsec->lock);
 
-	if (!selinux_state.initialized) {
+	if (!selinux_initialized(&selinux_state)) {
 		if (!opts) {
 			/* Defer initialization until selinux_complete_init,
 			   after the initial policy is loaded and the security
@@ -929,7 +929,7 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
 	 * if the parent was able to be mounted it clearly had no special lsm
 	 * mount options.  thus we can safely deal with this superblock later
 	 */
-	if (!selinux_state.initialized)
+	if (!selinux_initialized(&selinux_state))
 		return 0;
 
 	/*
@@ -1104,7 +1104,7 @@ static int selinux_sb_show_options(struct seq_file *m, struct super_block *sb)
 	if (!(sbsec->flags & SE_SBINITIALIZED))
 		return 0;
 
-	if (!selinux_state.initialized)
+	if (!selinux_initialized(&selinux_state))
 		return 0;
 
 	if (sbsec->flags & FSCONTEXT_MNT) {
@@ -2921,7 +2921,8 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 		isec->initialized = LABEL_INITIALIZED;
 	}
 
-	if (!selinux_state.initialized || !(sbsec->flags & SBLABEL_MNT))
+	if (!selinux_initialized(&selinux_state) ||
+	    !(sbsec->flags & SBLABEL_MNT))
 		return -EOPNOTSUPP;
 
 	if (name)
@@ -3144,7 +3145,7 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
 		return dentry_has_perm(current_cred(), dentry, FILE__SETATTR);
 	}
 
-	if (!selinux_state.initialized)
+	if (!selinux_initialized(&selinux_state))
 		return (inode_owner_or_capable(inode) ? 0 : -EPERM);
 
 	sbsec = inode->i_sb->s_security;
@@ -3230,7 +3231,7 @@ static void selinux_inode_post_setxattr(struct dentry *dentry, const char *name,
 		return;
 	}
 
-	if (!selinux_state.initialized) {
+	if (!selinux_initialized(&selinux_state)) {
 		/* If we haven't even been initialized, then we can't validate
 		 * against a policy, so leave the label as invalid. It may
 		 * resolve to a valid label on the next revalidation try if
@@ -7300,17 +7301,17 @@ static void selinux_nf_ip_exit(void)
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 int selinux_disable(struct selinux_state *state)
 {
-	if (state->initialized) {
+	if (selinux_initialized(state)) {
 		/* Not permitted after initial policy load. */
 		return -EINVAL;
 	}
 
-	if (state->disabled) {
+	if (selinux_disabled(state)) {
 		/* Only do this once. */
 		return -EINVAL;
 	}
 
-	state->disabled = 1;
+	selinux_mark_disabled(state);
 
 	pr_info("SELinux:  Disabled at runtime.\n");