LSM: generalize flag passing to security_capable

This patch provides a general mechanism for passing flags to the
security_capable LSM hook. It replaces the specific 'audit' flag that is
used to tell security_capable whether it should log an audit message for
the given capability check. The reason for generalizing this flag
passing is so we can add an additional flag that signifies whether
security_capable is being called by a setid syscall (which is needed by
the proposed SafeSetID LSM).

Signed-off-by: Micah Morton <mortonm@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

2 files changed, 15 insertions, 11 deletions

diff --git a/kernel/capability.c b/kernel/capability.c
index 1e1c0236f55b..7718d7dcadc7 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -299,7 +299,7 @@ bool has_ns_capability(struct task_struct *t,
 	int ret;
 
 	rcu_read_lock();
-	ret = security_capable(__task_cred(t), ns, cap);
+	ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
 	rcu_read_unlock();
 
 	return (ret == 0);
@@ -340,7 +340,7 @@ bool has_ns_capability_noaudit(struct task_struct *t,
 	int ret;
 
 	rcu_read_lock();
-	ret = security_capable_noaudit(__task_cred(t), ns, cap);
+	ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
 	rcu_read_unlock();
 
 	return (ret == 0);
@@ -363,7 +363,9 @@ bool has_capability_noaudit(struct task_struct *t, int cap)
 	return has_ns_capability_noaudit(t, &init_user_ns, cap);
 }
 
-static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
+static bool ns_capable_common(struct user_namespace *ns,
+			      int cap,
+			      unsigned int opts)
 {
 	int capable;
 
@@ -372,8 +374,7 @@ static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
 		BUG();
 	}
 
-	capable = audit ? security_capable(current_cred(), ns, cap) :
-			  security_capable_noaudit(current_cred(), ns, cap);
+	capable = security_capable(current_cred(), ns, cap, opts);
 	if (capable == 0) {
 		current->flags |= PF_SUPERPRIV;
 		return true;
@@ -394,7 +395,7 @@ static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
  */
 bool ns_capable(struct user_namespace *ns, int cap)
 {
-	return ns_capable_common(ns, cap, true);
+	return ns_capable_common(ns, cap, CAP_OPT_NONE);
 }
 EXPORT_SYMBOL(ns_capable);
 
@@ -412,7 +413,7 @@ EXPORT_SYMBOL(ns_capable);
  */
 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
 {
-	return ns_capable_common(ns, cap, false);
+	return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
 }
 EXPORT_SYMBOL(ns_capable_noaudit);
 
@@ -448,10 +449,11 @@ EXPORT_SYMBOL(capable);
 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
 		     int cap)
 {
+
 	if (WARN_ON_ONCE(!cap_valid(cap)))
 		return false;
 
-	if (security_capable(file->f_cred, ns, cap) == 0)
+	if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
 		return true;
 
 	return false;
@@ -500,10 +502,12 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
 {
 	int ret = 0;  /* An absent tracer adds no restrictions */
 	const struct cred *cred;
+
 	rcu_read_lock();
 	cred = rcu_dereference(tsk->ptracer_cred);
 	if (cred)
-		ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
+		ret = security_capable(cred, ns, CAP_SYS_PTRACE,
+				       CAP_OPT_NOAUDIT);
 	rcu_read_unlock();
 	return (ret == 0);
 }
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index d7f538847b84..38a77800def6 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -443,8 +443,8 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
 	 * behavior of privileged children.
 	 */
 	if (!task_no_new_privs(current) &&
-	    security_capable_noaudit(current_cred(), current_user_ns(),
-				     CAP_SYS_ADMIN) != 0)
+	    security_capable(current_cred(), current_user_ns(),
+				     CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0)
 		return ERR_PTR(-EACCES);
 
 	/* Allocate a new seccomp_filter */