1 files changed, 64 insertions, 1 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index b3c76e815d66..85439abdbc80 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -114,6 +114,13 @@ struct thread_group_cred {
  */
 struct cred {
         atomic_t        usage;
+#ifdef CONFIG_DEBUG_CREDENTIALS
+        atomic_t        subscribers;    /* number of processes subscribed */
+        void            *put_addr;
+        unsigned        magic;
+#define CRED_MAGIC      0x43736564
+#define CRED_MAGIC_DEAD 0x44656144
+#endif
         uid_t           uid;            /* real UID of the task */
         gid_t           gid;            /* real GID of the task */
         uid_t           suid;           /* saved UID of the task */
@@ -143,6 +150,7 @@ struct cred {
 };
 
 extern void __put_cred(struct cred *);
+extern void exit_creds(struct task_struct *);
 extern int copy_creds(struct task_struct *, unsigned long);
 extern struct cred *prepare_creds(void);
 extern struct cred *prepare_exec_creds(void);
@@ -158,6 +166,60 @@ extern int set_security_override_from_ctx(struct cred *, const char *);
 extern int set_create_files_as(struct cred *, struct inode *);
 extern void __init cred_init(void);
 
+/*
+ * check for validity of credentials
+ */
+#ifdef CONFIG_DEBUG_CREDENTIALS
+extern void __invalid_creds(const struct cred *, const char *, unsigned);
+extern void __validate_process_creds(struct task_struct *,
+                                     const char *, unsigned);
+
+static inline bool creds_are_invalid(const struct cred *cred)
+{
+        if (cred->magic != CRED_MAGIC)
+                return true;
+        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;
+#endif
+        return false;
+}
+
+static inline void __validate_creds(const struct cred *cred,
+                                    const char *file, unsigned line)
+{
+        if (unlikely(creds_are_invalid(cred)))
+                __invalid_creds(cred, file, line);
+}
+
+#define validate_creds(cred)                            \
+do {                                                    \
+        __validate_creds((cred), __FILE__, __LINE__);   \
+} while(0)
+
+#define validate_process_creds()                                \
+do {                                                            \
+        __validate_process_creds(current, __FILE__, __LINE__);  \
+} while(0)
+
+extern void validate_creds_for_do_exit(struct task_struct *);
+#else
+static inline void validate_creds(const struct cred *cred)
+{
+}
+static inline void validate_creds_for_do_exit(struct task_struct *tsk)
+{
+}
+static inline void validate_process_creds(void)
+{
+}
+#endif
+
 /**
  * get_new_cred - Get a reference on a new set of credentials
  * @cred: The new credentials to reference
@@ -187,6 +249,7 @@ static inline struct cred *get_new_cred(struct cred *cred)
 static inline const struct cred *get_cred(const struct cred *cred)
 {
         struct cred *nonconst_cred = (struct cred *) cred;
+        validate_creds(cred);
         return get_new_cred(nonconst_cred);
 }
 
@@ -205,7 +268,7 @@ static inline void put_cred(const struct cred *_cred)
 {
         struct cred *cred = (struct cred *) _cred;
 
-        BUG_ON(atomic_read(&(cred)->usage) <= 0);
+        validate_creds(cred);
         if (atomic_dec_and_test(&(cred)->usage))
                 __put_cred(cred);
 }