From: NeilBrown <neilb@suse.com>
Date: Mon, 3 Dec 2018 11:30:30 +1100
Subject: [PATCH] cred: allow get_cred() and put_cred() to be given NULL.
Git-commit: f06bc03339ad4c1baa964a5f0606247ac1c3c50b
Patch-mainline: v5.0-rc1
References: bsc#1209887

It is common practice for helpers like this to silently,
accept a NULL pointer.
get_rpccred() and put_rpccred() used by NFS act this way
and using the same interface will ease the conversion
for NFS, and simplify the resulting code.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 include/linux/cred.h |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -231,7 +231,7 @@ static inline struct cred *get_new_cred(
  * @cred: The credentials to reference
  *
  * Get a reference on the specified set of credentials.  The caller must
- * release the reference.
+ * release the reference.  If %NULL is passed, it is returned with no action.
  *
  * This is used to deal with a committed set of credentials.  Although the
  * pointer is const, this will temporarily discard the const and increment the
@@ -242,6 +242,8 @@ static inline struct cred *get_new_cred(
 static inline const struct cred *get_cred(const struct cred *cred)
 {
 	struct cred *nonconst_cred = (struct cred *) cred;
+	if (!cred)
+		return cred;
 	validate_creds(cred);
 	return get_new_cred(nonconst_cred);
 }
@@ -251,7 +253,7 @@ static inline const struct cred *get_cre
  * @cred: The credentials to release
  *
  * Release a reference to a set of credentials, deleting them when the last ref
- * is released.
+ * is released.  If %NULL is passed, nothing is done.
  *
  * This takes a const pointer to a set of credentials because the credentials
  * on task_struct are attached by const pointers to prevent accidental
@@ -261,9 +263,11 @@ static inline void put_cred(const struct
 {
 	struct cred *cred = (struct cred *) _cred;
 
-	validate_creds(cred);
-	if (atomic_dec_and_test(&(cred)->usage))
-		__put_cred(cred);
+	if (cred) {
+		validate_creds(cred);
+		if (atomic_dec_and_test(&(cred)->usage))
+			__put_cred(cred);
+	}
 }
 
 /**