Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 7eed610..18639c0 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -1,12 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 /* Credentials management - see Documentation/security/credentials.rst
  *
  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
- * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
  */
 
 #ifndef _LINUX_CRED_H
@@ -15,7 +11,6 @@
 #include <linux/capability.h>
 #include <linux/init.h>
 #include <linux/key.h>
-#include <linux/selinux.h>
 #include <linux/atomic.h>
 #include <linux/uidgid.h>
 #include <linux/sched.h>
@@ -139,7 +134,7 @@
 #ifdef CONFIG_KEYS
 	unsigned char	jit_keyring;	/* default keyring to attach requested
 					 * keys to */
-	struct key __rcu *session_keyring; /* keyring inherited over fork */
+	struct key	*session_keyring; /* keyring inherited over fork */
 	struct key	*process_keyring; /* keyring private to this process */
 	struct key	*thread_keyring; /* keyring private to this thread */
 	struct key	*request_key_auth; /* assumed request_key authority */
@@ -150,7 +145,11 @@
 	struct user_struct *user;	/* real user ID subscription */
 	struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 	struct group_info *group_info;	/* supplementary groups for euid/fsgid */
-	struct rcu_head	rcu;		/* RCU deletion hook */
+	/* RCU deletion */
+	union {
+		int non_rcu;			/* Can we skip RCU deletion? */
+		struct rcu_head	rcu;		/* RCU deletion hook */
+	};
 } __randomize_layout;
 
 extern void __put_cred(struct cred *);
@@ -169,6 +168,7 @@
 extern int set_security_override(struct cred *, u32);
 extern int set_security_override_from_ctx(struct cred *, const char *);
 extern int set_create_files_as(struct cred *, struct inode *);
+extern int cred_fscmp(const struct cred *, const struct cred *);
 extern void __init cred_init(void);
 
 /*
@@ -236,7 +236,7 @@
  * @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
@@ -247,16 +247,31 @@
 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);
+	nonconst_cred->non_rcu = 0;
 	return get_new_cred(nonconst_cred);
 }
 
+static inline const struct cred *get_cred_rcu(const struct cred *cred)
+{
+	struct cred *nonconst_cred = (struct cred *) cred;
+	if (!cred)
+		return NULL;
+	if (!atomic_inc_not_zero(&nonconst_cred->usage))
+		return NULL;
+	validate_creds(cred);
+	nonconst_cred->non_rcu = 0;
+	return cred;
+}
+
 /**
  * put_cred - Release a reference to a set of credentials
  * @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
@@ -266,9 +281,11 @@
 {
 	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);
+	}
 }
 
 /**
@@ -369,7 +386,6 @@
 #define current_fsgid() 	(current_cred_xxx(fsgid))
 #define current_cap()		(current_cred_xxx(cap_effective))
 #define current_user()		(current_cred_xxx(user))
-#define current_security()	(current_cred_xxx(security))
 
 extern struct user_namespace init_user_ns;
 #ifdef CONFIG_USER_NS