libnvme: fix NULL handle dereference in discovery and identify paths

libnvme/src/nvme/fabrics.c

@@ -1389,6 +1389,12 @@ static int nvme_discovery_log(libnvme_ctrl_t ctrl,
 	struct libnvme_transport_handle *hdl;
 
 	hdl = libnvme_ctrl_get_transport_handle(ctrl);
+	if (!hdl) {
+		libnvme_msg(ctx, LIBNVME_LOG_DEBUG,
+			 "%s: failed to get discovery log, device not accessible\n",
+			 name);
+		return -ENODEV;
+	}
 	struct libnvme_passthru_cmd cmd;
 
 	log = __libnvme_alloc(sizeof(*log));
@@ -1641,6 +1647,13 @@ static int nvmf_dim(libnvme_ctrl_t c, enum nvmf_dim_tas tas, __u8 trtype,
 	__u32 tel;
 	int ret;
 
+	if (!hdl) {
+		libnvme_msg(ctx, LIBNVME_LOG_DEBUG,
+			 "%s: failed to perform DIM, device not accessible\n",
+			 c->name);
+		return -ENODEV;
+	}
+
 	if (!c->s) {
 		libnvme_msg(ctx, LIBNVME_LOG_ERR,
 			 "%s: failed to perform DIM. subsystem undefined.\n",

libnvme/src/nvme/nvme-cmds.c

@@ -36,6 +36,8 @@ __public int libnvme_get_log(struct libnvme_transport_handle *hdl,
 		struct libnvme_passthru_cmd *cmd, bool rae,
 		__u32 xfer_len)
 {
+	if (!hdl)
+		return -ENODEV; /* safety net; callers must validate hdl */
 	__u64 offset = 0, xfer, data_len = cmd->data_len;
 	__u64 start = (__u64)cmd->cdw13 << 32 | cmd->cdw12;
 	__u64 lpo;

libnvme/src/nvme/tree.c

@@ -1497,6 +1497,12 @@ __public int libnvme_ctrl_identify(libnvme_ctrl_t c, struct nvme_id_ctrl *id)
 		libnvme_ctrl_get_transport_handle(c);
 	struct libnvme_passthru_cmd cmd;
 
+	if (!hdl) {
+		libnvme_msg(c->ctx, LIBNVME_LOG_DEBUG,
+			 "%s: failed to identify ctrl, device not accessible\n",
+			 c->name);
+		return -ENODEV;
+	}
 	nvme_init_identify_ctrl(&cmd, id);
 	return libnvme_submit_admin_passthru(hdl, &cmd);
 }