smack: differentiate between subjective and objective task credentials

With the split of the security_task_getsecid() into subjective and
objective variants it's time to update Smack to ensure it is using
the correct task creds.
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/smack/smack.h

@@ -383,7 +383,23 @@ static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
 	return tsp->smk_task;
 }
 
-static inline struct smack_known *smk_of_task_struct(
+static inline struct smack_known *smk_of_task_struct_subj(
+						const struct task_struct *t)
+{
+	struct smack_known *skp;
+	const struct cred *cred;
+
+	rcu_read_lock();
+
+	cred = rcu_dereference(t->cred);
+	skp = smk_of_task(smack_cred(cred));
+
+	rcu_read_unlock();
+
+	return skp;
+}
+
+static inline struct smack_known *smk_of_task_struct_obj(
 						const struct task_struct *t)
 {
 	struct smack_known *skp;

security/smack/smack_lsm.c

@@ -159,7 +159,7 @@ static int smk_bu_current(char *note, struct smack_known *oskp,
 static int smk_bu_task(struct task_struct *otp, int mode, int rc)
 {
 	struct task_smack *tsp = smack_cred(current_cred());
-	struct smack_known *smk_task = smk_of_task_struct(otp);
+	struct smack_known *smk_task = smk_of_task_struct_obj(otp);
 	char acc[SMK_NUM_ACCESS_TYPE + 1];
 
 	if (rc <= 0)
@@ -479,7 +479,7 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
 {
 	struct smack_known *skp;
 
-	skp = smk_of_task_struct(ctp);
+	skp = smk_of_task_struct_obj(ctp);
 
 	return smk_ptrace_rule_check(current, skp, mode, __func__);
 }
@@ -2033,7 +2033,7 @@ static int smk_curacc_on_task(struct task_struct *p, int access,
 				const char *caller)
 {
 	struct smk_audit_info ad;
-	struct smack_known *skp = smk_of_task_struct(p);
+	struct smack_known *skp = smk_of_task_struct_subj(p);
 	int rc;
 
 	smk_ad_init(&ad, caller, LSM_AUDIT_DATA_TASK);
@@ -2078,15 +2078,29 @@ static int smack_task_getsid(struct task_struct *p)
 }
 
 /**
- * smack_task_getsecid - get the secid of the task
- * @p: the object task
+ * smack_task_getsecid_subj - get the subjective secid of the task
+ * @p: the task
  * @secid: where to put the result
  *
- * Sets the secid to contain a u32 version of the smack label.
+ * Sets the secid to contain a u32 version of the task's subjective smack label.
+ */
+static void smack_task_getsecid_subj(struct task_struct *p, u32 *secid)
+{
+	struct smack_known *skp = smk_of_task_struct_subj(p);
+
+	*secid = skp->smk_secid;
+}
+
+/**
+ * smack_task_getsecid_obj - get the objective secid of the task
+ * @p: the task
+ * @secid: where to put the result
+ *
+ * Sets the secid to contain a u32 version of the task's objective smack label.
  */
-static void smack_task_getsecid(struct task_struct *p, u32 *secid)
+static void smack_task_getsecid_obj(struct task_struct *p, u32 *secid)
 {
-	struct smack_known *skp = smk_of_task_struct(p);
+	struct smack_known *skp = smk_of_task_struct_obj(p);
 
 	*secid = skp->smk_secid;
 }
@@ -2174,7 +2188,7 @@ static int smack_task_kill(struct task_struct *p, struct kernel_siginfo *info,
 {
 	struct smk_audit_info ad;
 	struct smack_known *skp;
-	struct smack_known *tkp = smk_of_task_struct(p);
+	struct smack_known *tkp = smk_of_task_struct_obj(p);
 	int rc;
 
 	if (!sig)
@@ -2212,7 +2226,7 @@ static int smack_task_kill(struct task_struct *p, struct kernel_siginfo *info,
 static void smack_task_to_inode(struct task_struct *p, struct inode *inode)
 {
 	struct inode_smack *isp = smack_inode(inode);
-	struct smack_known *skp = smk_of_task_struct(p);
+	struct smack_known *skp = smk_of_task_struct_obj(p);
 
 	isp->smk_inode = skp;
 	isp->smk_flags |= SMK_INODE_INSTANT;
@@ -3483,7 +3497,7 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
  */
 static int smack_getprocattr(struct task_struct *p, char *name, char **value)
 {
-	struct smack_known *skp = smk_of_task_struct(p);
+	struct smack_known *skp = smk_of_task_struct_subj(p);
 	char *cp;
 	int slen;
 
@@ -4759,8 +4773,8 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
 	LSM_HOOK_INIT(task_getpgid, smack_task_getpgid),
 	LSM_HOOK_INIT(task_getsid, smack_task_getsid),
-	LSM_HOOK_INIT(task_getsecid_subj, smack_task_getsecid),
-	LSM_HOOK_INIT(task_getsecid_obj, smack_task_getsecid),
+	LSM_HOOK_INIT(task_getsecid_subj, smack_task_getsecid_subj),
+	LSM_HOOK_INIT(task_getsecid_obj, smack_task_getsecid_obj),
 	LSM_HOOK_INIT(task_setnice, smack_task_setnice),
 	LSM_HOOK_INIT(task_setioprio, smack_task_setioprio),
 	LSM_HOOK_INIT(task_getioprio, smack_task_getioprio),