commit c1a85a00ea66cb6f0bd0f14e47c28c2b0999799f
author Micah Morton <mortonm@chromium.org> Mon Jan 07 16:10:53 2019 -0800
committer James Morris <james.morris@microsoft.com> Thu Jan 10 14:16:06 2019 -0800
tree 310c082e0b41d2d3ff8b619553ed5e45ad244862
parent 2233975cd7927672525361c4c6eebc0b8d018a74

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>

kernel/capability.c

diff --git a/kernel/capability.c b/kernel/capability.c
index 1e1c023..7718d7d 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -299,7 +299,7 @@
 	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 @@
 	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 @@
 	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 @@
 		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 @@
  */
 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 @@
  */
 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 @@
 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 @@
 {
 	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);
 }