Patch "cifs: Create dedicated keyring for spnego operations" has been added to the 4.4-stable tree

@@ -24,10 +24,13 @@
 #include <linux/string.h>
 #include <keys/user-type.h>
 #include <linux/key-type.h>
+#include <linux/keyctl.h>
 #include <linux/inet.h>
 #include "cifsglob.h"
 #include "cifs_spnego.h"
 #include "cifs_debug.h"
+#include "cifsproto.h"
+static const struct cred *spnego_cred;
 
 /* create a new cifs key */
 static int

@@ -102,6 +105,7 @@ cifs_get_spnego_key(struct cifs_ses *ses
 	size_t desc_len;
 	struct key *spnego_key;
 	const char *hostname = server->hostname;
+	const struct cred *saved_cred;
 
 	/* length of fields (with semicolons): ver=0xyz ip4=ipaddress
 	   host=hostname sec=mechanism uid=0xFF user=username */

@@ -163,7 +167,9 @@ cifs_get_spnego_key(struct cifs_ses *ses
 	sprintf(dp, ";pid=0x%x", current->pid);
 
 	cifs_dbg(FYI, "key description = %s\n", description);
+	saved_cred = override_creds(spnego_cred);
 	spnego_key = request_key(&cifs_spnego_key_type, description, "");
+	revert_creds(saved_cred);
 
 #ifdef CONFIG_CIFS_DEBUG2
 	if (cifsFYI && !IS_ERR(spnego_key)) {

@@ -177,3 +183,64 @@ out:
 	kfree(description);
 	return spnego_key;
 }
+
+int
+init_cifs_spnego(void)
+{
+	struct cred *cred;
+	struct key *keyring;
+	int ret;
+
+	cifs_dbg(FYI, "Registering the %s key type\n",
+		 cifs_spnego_key_type.name);
+
+	/*
+	 * Create an override credential set with special thread keyring for
+	 * spnego upcalls.
+	 */
+
+	cred = prepare_kernel_cred(NULL);
+	if (!cred)
+		return -ENOMEM;
+
+	keyring = keyring_alloc(".cifs_spnego",
+				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
+				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				KEY_USR_VIEW | KEY_USR_READ,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(keyring)) {
+		ret = PTR_ERR(keyring);
+		goto failed_put_cred;
+	}
+
+	ret = register_key_type(&cifs_spnego_key_type);
+	if (ret < 0)
+		goto failed_put_key;
+
+	/*
+	 * instruct request_key() to use this special keyring as a cache for
+	 * the results it looks up
+	 */
+	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
+	cred->thread_keyring = keyring;
+	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+	spnego_cred = cred;
+
+	cifs_dbg(FYI, "cifs spnego keyring: %d\n", key_serial(keyring));
+	return 0;
+
+failed_put_key:
+	key_put(keyring);
+failed_put_cred:
+	put_cred(cred);
+	return ret;
+}
+
+void
+exit_cifs_spnego(void)
+{
+	key_revoke(spnego_cred->thread_keyring);
+	unregister_key_type(&cifs_spnego_key_type);
+	put_cred(spnego_cred);
+	cifs_dbg(FYI, "Unregistered %s key type\n", cifs_spnego_key_type.name);
+}

@@ -1233,7 +1233,7 @@ init_cifs(void)
 		goto out_destroy_mids;
 
 #ifdef CONFIG_CIFS_UPCALL
-	rc = register_key_type(&cifs_spnego_key_type);
+	rc = init_cifs_spnego();
 	if (rc)
 		goto out_destroy_request_bufs;
 #endif /* CONFIG_CIFS_UPCALL */

@@ -1256,7 +1256,7 @@ out_init_cifs_idmap:
 out_register_key_type:
 #endif
 #ifdef CONFIG_CIFS_UPCALL
-	unregister_key_type(&cifs_spnego_key_type);
+	exit_cifs_spnego();
 out_destroy_request_bufs:
 #endif
 	cifs_destroy_request_bufs();

@@ -60,6 +60,8 @@ do {								\
 } while (0)
 extern int init_cifs_idmap(void);
 extern void exit_cifs_idmap(void);
+extern int init_cifs_spnego(void);
+extern void exit_cifs_spnego(void);
 extern char *build_path_from_dentry(struct dentry *);
 extern char *cifs_build_path_to_root(struct smb_vol *vol,
 				     struct cifs_sb_info *cifs_sb,