Add a new capable interface that will be used by systems that use audit to

make an A or B type decision instead of a security decision.  Currently
this is the case at least for filesystems when deciding if a process can use
the reserved 'root' blocks and for the case of things like the oom
algorithm determining if processes are root processes and should be less
likely to be killed.  These types of security system requests should not be
audited or logged since they are not really security decisions.  It would be
possible to solve this problem like the vm_enough_memory security check did
by creating a new LSM interface and moving all of the policy into that
interface but proves the needlessly bloat the LSM and provide complex
indirection.

This merely allows those decisions to be made where they belong and to not
flood logs or printk with denials for thing that are not security decisions.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

2 files changed, 16 insertions, 3 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 0f195018110..b313ba1dd5d 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -521,6 +521,8 @@ extern const kernel_cap_t __cap_init_eff_set;
 
 kernel_cap_t cap_set_effective(const kernel_cap_t pE_new);
 
+extern int security_capable(struct task_struct *t, int cap);
+extern int security_capable_noaudit(struct task_struct *t, int cap);
 /**
  * has_capability - Determine if a task has a superior capability available
  * @t: The task in question
@@ -532,6 +534,7 @@ kernel_cap_t cap_set_effective(const kernel_cap_t pE_new);
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 #define has_capability(t, cap) (security_capable((t), (cap)) == 0)
+#define has_capability_noaudit(t, cap) (security_capable_noaudit((t), (cap)) == 0)
 
 extern int capable(int cap);
 
diff --git a/include/linux/security.h b/include/linux/security.h
index c13f1cec9ab..5fe28a671cd 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -37,6 +37,10 @@
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
 
+/* If capable should audit the security request */
+#define SECURITY_CAP_NOAUDIT 0
+#define SECURITY_CAP_AUDIT 1
+
 struct ctl_table;
 struct audit_krule;
 
@@ -44,7 +48,7 @@ struct audit_krule;
  * These functions are in security/capability.c and are used
  * as the default capabilities functions
  */
-extern int cap_capable(struct task_struct *tsk, int cap);
+extern int cap_capable(struct task_struct *tsk, int cap, int audit);
 extern int cap_settime(struct timespec *ts, struct timezone *tz);
 extern int cap_ptrace_may_access(struct task_struct *child, unsigned int mode);
 extern int cap_ptrace_traceme(struct task_struct *parent);
@@ -1307,7 +1311,7 @@ struct security_operations {
 			    kernel_cap_t *effective,
 			    kernel_cap_t *inheritable,
 			    kernel_cap_t *permitted);
-	int (*capable) (struct task_struct *tsk, int cap);
+	int (*capable) (struct task_struct *tsk, int cap, int audit);
 	int (*acct) (struct file *file);
 	int (*sysctl) (struct ctl_table *table, int op);
 	int (*quotactl) (int cmds, int type, int id, struct super_block *sb);
@@ -1577,6 +1581,7 @@ void security_capset_set(struct task_struct *target,
 			 kernel_cap_t *inheritable,
 			 kernel_cap_t *permitted);
 int security_capable(struct task_struct *tsk, int cap);
+int security_capable_noaudit(struct task_struct *tsk, int cap);
 int security_acct(struct file *file);
 int security_sysctl(struct ctl_table *table, int op);
 int security_quotactl(int cmds, int type, int id, struct super_block *sb);
@@ -1782,7 +1787,12 @@ static inline void security_capset_set(struct task_struct *target,
 
 static inline int security_capable(struct task_struct *tsk, int cap)
 {
-	return cap_capable(tsk, cap);
+	return cap_capable(tsk, cap, SECURITY_CAP_AUDIT);
+}
+
+static inline int security_capable_noaudit(struct task_struct *tsk, int cap)
+{
+	return cap_capable(tsk, cap, SECURITY_CAP_NOAUDIT);
 }
 
 static inline int security_acct(struct file *file)