CRED: Use RCU to access another task's creds and to release a task's own creds

Use RCU to access another task's creds and to release a task's own creds.
This means that it will be possible for the credentials of a task to be
replaced without another task (a) requiring a full lock to read them, and (b)
seeing deallocated memory.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 4221ec6000c1..166ce4ddba64 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -147,8 +147,9 @@ static inline struct cred *get_cred(struct cred *cred)
  * Release a reference to a set of credentials, deleting them when the last ref
  * is released.
  */
-static inline void put_cred(struct cred *cred)
+static inline void put_cred(const struct cred *_cred)
 {
+        struct cred *cred = (struct cred *) _cred;
         if (atomic_dec_and_test(&(cred)->usage))
                 __put_cred(cred);
 }