Creds: creds->security can be NULL is selinux is disabled

__validate_process_creds should check if selinux is actually enabled before
running tests on the selinux portion of the credentials struct.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

2 files changed, 17 insertions, 5 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 24520a539c6f..fb371601a3b4 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -15,6 +15,7 @@
 #include <linux/capability.h>
 #include <linux/init.h>
 #include <linux/key.h>
+#include <linux/selinux.h>
 #include <asm/atomic.h>
 
 struct user_struct;
@@ -182,11 +183,13 @@ static inline bool creds_are_invalid(const struct cred *cred)
         if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
                 return true;
 #ifdef CONFIG_SECURITY_SELINUX
-        if ((unsigned long) cred->security < PAGE_SIZE)
-                return true;
-        if ((*(u32*)cred->security & 0xffffff00) ==
-            (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
-                return true;
+        if (selinux_is_enabled()) {
+                if ((unsigned long) cred->security < PAGE_SIZE)
+                        return true;
+                if ((*(u32 *)cred->security & 0xffffff00) ==
+                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
+                        return true;
+        }
 #endif
         return false;
 }
diff --git a/include/linux/selinux.h b/include/linux/selinux.h
index 20f965d4b041..223d06a6feb1 100644
--- a/include/linux/selinux.h
+++ b/include/linux/selinux.h
@@ -61,6 +61,11 @@ void selinux_secmark_refcount_inc(void);
  *     existing SECMARK targets has been removed/flushed.
  */
 void selinux_secmark_refcount_dec(void);
+
+/**
+ * selinux_is_enabled - is SELinux enabled?
+ */
+bool selinux_is_enabled(void);
 #else
 
 static inline int selinux_string_to_sid(const char *str, u32 *sid)
@@ -84,6 +89,10 @@ static inline void selinux_secmark_refcount_dec(void)
         return;
 }
 
+static bool selinux_is_enabled(void)
+{
+        return false;
+}
 #endif  /* CONFIG_SECURITY_SELINUX */
 
 #endif /* _LINUX_SELINUX_H */