nvme-keyring: register '.nvme' keyring

Register a '.nvme' keyring to hold keys for TLS and DH-HMAC-CHAP and
add a new config option NVME_KEYRING.
We need a separate keyring for NVMe as the configuration is done
via individual commands (eg for configfs), and the usual per-session
or per-process keyrings can't be used.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/common/Kconfig

@@ -2,3 +2,7 @@
 
 config NVME_COMMON
        tristate
+
+config NVME_KEYRING
+       bool
+       select KEYS

drivers/nvme/common/Makefile

@@ -4,4 +4,5 @@ ccflags-y			+= -I$(src)
 
 obj-$(CONFIG_NVME_COMMON)	+= nvme-common.o
 
-nvme-common-y			+= auth.o
+nvme-common-$(CONFIG_NVME_AUTH)	+= auth.o
+nvme-common-$(CONFIG_NVME_KEYRING) += keyring.o

drivers/nvme/common/keyring.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023 Hannes Reinecke, SUSE Labs
+ */
+
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/key-type.h>
+#include <keys/user-type.h>
+#include <linux/nvme.h>
+
+static struct key *nvme_keyring;
+
+key_serial_t nvme_keyring_id(void)
+{
+	return nvme_keyring->serial;
+}
+EXPORT_SYMBOL_GPL(nvme_keyring_id);
+
+int nvme_keyring_init(void)
+{
+	nvme_keyring = keyring_alloc(".nvme",
+				     GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+				     current_cred(),
+				     (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				     (KEY_USR_ALL & ~KEY_USR_SETATTR),
+				     KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(nvme_keyring))
+		return PTR_ERR(nvme_keyring);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvme_keyring_init);
+
+void nvme_keyring_exit(void)
+{
+	key_revoke(nvme_keyring);
+	key_put(nvme_keyring);
+}
+EXPORT_SYMBOL_GPL(nvme_keyring_exit);