[PATCH v2 3/3] nvme-fabrics: prevent overriding of existing host

[Max Gurtovoy]

When first connecting a target using the "default" host parameters,
setting the hostid from the command line during a subsequent connection
establishment would override the "default" hostid parameter. This would
cause an existing connection that is already using the host definitions
to lose its hostid.

To address this issue, the code has been modified to allow only 1:1
mapping between hostnqn and hostid. This will maintain unambiguous host
identification. Any non 1:1 mapping will be rejected during connection
establishment.

Tested-by: Noam Gottlieb <ngottlieb at nvidia.com>
Reviewed-by: Israel Rukshin <israelr at nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy at nvidia.com>
---

changes from v1:
- address comments from Christoph
- allow only 1:1 mapping between hostnqn and hostid
- add error prints in case we fail a connection for user to understand
  the reason of the failure

---
 drivers/nvme/host/fabrics.c | 98 ++++++++++++++++++++++++++-----------
 1 file changed, 70 insertions(+), 28 deletions(-)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 0c0172bdc4dc..f8e47c7d6188 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -21,35 +21,77 @@ static DEFINE_MUTEX(nvmf_hosts_mutex);
 
 static struct nvmf_host *nvmf_default_host;
 
-static struct nvmf_host *__nvmf_host_find(const char *hostnqn)
+/**
+ * __nvmf_host_find() - Find a matching to a previously created host
+ * @hostnqn: Host NQN to match
+ * @id: Host ID to match
+ *
+ * We have defined a host as how it is perceived by the target.
+ * Therefore, we don't allow different Host NQNs with the same Host ID.
+ * Similarly, we do not allow the usage of the same Host NQN with different
+ * Host IDs. This will maintain unambiguous host identification.
+ *
+ * Return: Returns host pointer on success, NULL in case of no match or
+ *         ERR_PTR(-EINVAL) in case of error match.
+ */
+static struct nvmf_host *__nvmf_host_find(const char *hostnqn, uuid_t *id)
 {
 	struct nvmf_host *host;
 
+	lockdep_assert_held(&nvmf_hosts_mutex);
+
 	list_for_each_entry(host, &nvmf_hosts, list) {
-		if (!strcmp(host->nqn, hostnqn))
-			return host;
+		if (!strcmp(host->nqn, hostnqn)) {
+			if (uuid_equal(&host->id, id)) {
+				// same hostnqn and hostid
+				return host;
+			} else {
+				pr_err("found same hostnqn %s but different hostid %pUb\n",
+				       hostnqn, id);
+				return ERR_PTR(-EINVAL);
+			}
+		} else if (uuid_equal(&host->id, id)) {
+			// same hostid but different hostnqn
+			pr_err("found same hostid %pUb but different hostnqn %s\n",
+			        id, hostnqn);
+			return ERR_PTR(-EINVAL);
+		}
 	}
 
 	return NULL;
 }
 
-static struct nvmf_host *nvmf_host_add(const char *hostnqn)
+static struct nvmf_host *nvmf_host_alloc(const char *hostnqn, uuid_t *id)
+{
+	struct nvmf_host *host;
+
+	host = kmalloc(sizeof(*host), GFP_KERNEL);
+	if (!host)
+		return NULL;
+
+	kref_init(&host->ref);
+	uuid_copy(&host->id, id);
+	strscpy(host->nqn, hostnqn, NVMF_NQN_SIZE);
+
+	return host;
+}
+
+static struct nvmf_host *nvmf_host_add(const char *hostnqn, uuid_t *id)
 {
 	struct nvmf_host *host;
 
 	mutex_lock(&nvmf_hosts_mutex);
-	host = __nvmf_host_find(hostnqn);
-	if (host) {
+	host = __nvmf_host_find(hostnqn, id);
+	if (IS_ERR(host)) {
+		goto out_unlock;
+	} else if (host) {
 		kref_get(&host->ref);
 		goto out_unlock;
 	}
 
-	host = kmalloc(sizeof(*host), GFP_KERNEL);
+	host = nvmf_host_alloc(hostnqn, id);
 	if (!host)
-		goto out_unlock;
-
-	kref_init(&host->ref);
-	strscpy(host->nqn, hostnqn, NVMF_NQN_SIZE);
+		return ERR_PTR(-ENOMEM);
 
 	list_add_tail(&host->list, &nvmf_hosts);
 out_unlock:
@@ -60,16 +102,17 @@ static struct nvmf_host *nvmf_host_add(const char *hostnqn)
 static struct nvmf_host *nvmf_host_default(void)
 {
 	struct nvmf_host *host;
+	char nqn[NVMF_NQN_SIZE];
+	uuid_t id;
 
-	host = kmalloc(sizeof(*host), GFP_KERNEL);
+	uuid_gen(&id);
+	snprintf(nqn, NVMF_NQN_SIZE,
+		"nqn.2014-08.org.nvmexpress:uuid:%pUb", &id);
+
+	host = nvmf_host_alloc(nqn, &id);
 	if (!host)
 		return NULL;
 
-	kref_init(&host->ref);
-	uuid_gen(&host->id);
-	snprintf(host->nqn, NVMF_NQN_SIZE,
-		"nqn.2014-08.org.nvmexpress:uuid:%pUb", &host->id);
-
 	mutex_lock(&nvmf_hosts_mutex);
 	list_add_tail(&host->list, &nvmf_hosts);
 	mutex_unlock(&nvmf_hosts_mutex);
@@ -633,6 +676,7 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 	size_t nqnlen  = 0;
 	int ctrl_loss_tmo = NVMF_DEF_CTRL_LOSS_TMO;
 	uuid_t hostid;
+	char hostnqn[NVMF_NQN_SIZE];
 
 	/* Set defaults */
 	opts->queue_size = NVMF_DEF_QUEUE_SIZE;
@@ -649,7 +693,9 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 	if (!options)
 		return -ENOMEM;
 
-	uuid_gen(&hostid);
+	/* use default host if not given by user space */
+	uuid_copy(&hostid, &nvmf_default_host->id);
+	strscpy(hostnqn, nvmf_default_host->nqn, NVMF_NQN_SIZE);
 
 	while ((p = strsep(&o, ",\n")) != NULL) {
 		if (!*p)
@@ -795,12 +841,8 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 				ret = -EINVAL;
 				goto out;
 			}
-			opts->host = nvmf_host_add(p);
+			strscpy(hostnqn, p, NVMF_NQN_SIZE);
 			kfree(p);
-			if (!opts->host) {
-				ret = -ENOMEM;
-				goto out;
-			}
 			break;
 		case NVMF_OPT_RECONNECT_DELAY:
 			if (match_int(args, &token)) {
@@ -957,13 +999,13 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 				opts->fast_io_fail_tmo, ctrl_loss_tmo);
 	}
 
-	if (!opts->host) {
-		kref_get(&nvmf_default_host->ref);
-		opts->host = nvmf_default_host;
+	opts->host = nvmf_host_add(hostnqn, &hostid);
+	if (IS_ERR(opts->host)) {
+		ret = PTR_ERR(opts->host);
+		opts->host = NULL;
+		goto out;
 	}
 
-	uuid_copy(&opts->host->id, &hostid);
-
 out:
 	kfree(options);
 	return ret;
-- 
2.18.1