dmaengine: idxd: Fix double free in idxd_setup_wqs()

The clean up in idxd_setup_wqs() has had a couple bugs because the error
handling is a bit subtle.  It's simpler to just re-write it in a cleaner
way.  The issues here are:

1) If "idxd->max_wqs" is <= 0 then we call put_device(conf_dev) when
   "conf_dev" hasn't been initialized.
2) If kzalloc_node() fails then again "conf_dev" is invalid.  It's
   either uninitialized or it points to the "conf_dev" from the
   previous iteration so it leads to a double free.

It's better to free partial loop iterations within the loop and then
the unwinding at the end can handle whole loop iterations.  I also
renamed the labels to describe what the goto does and not where the goto
was located.

Fixes: 3fd2f4b ("dmaengine: idxd: fix memory leak in error handling path of idxd_setup_wqs")
Reported-by: Colin Ian King <colin.i.king@gmail.com>
Closes: https://lore.kernel.org/all/20250811095836.1642093-1-colin.i.king@gmail.com/
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/aJnJW3iYTDDCj9sk@stanley.mountain
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: Dan Carpenter

drivers/dma/idxd/init.c

@@ -189,27 +189,30 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 	idxd->wq_enable_map = bitmap_zalloc_node(idxd->max_wqs, GFP_KERNEL, dev_to_node(dev));
 	if (!idxd->wq_enable_map) {
 		rc = -ENOMEM;
-		goto err_bitmap;
+		goto err_free_wqs;
 	}
 
 	for (i = 0; i < idxd->max_wqs; i++) {
 		wq = kzalloc_node(sizeof(*wq), GFP_KERNEL, dev_to_node(dev));
 		if (!wq) {
 			rc = -ENOMEM;
-			goto err;
+			goto err_unwind;
 		}
 
 		idxd_dev_set_type(&wq->idxd_dev, IDXD_DEV_WQ);
 		conf_dev = wq_confdev(wq);
 		wq->id = i;
 		wq->idxd = idxd;
-		device_initialize(wq_confdev(wq));
+		device_initialize(conf_dev);
 		conf_dev->parent = idxd_confdev(idxd);
 		conf_dev->bus = &dsa_bus_type;
 		conf_dev->type = &idxd_wq_device_type;
 		rc = dev_set_name(conf_dev, "wq%d.%d", idxd->id, wq->id);
-		if (rc < 0)
-			goto err;
+		if (rc < 0) {
+			put_device(conf_dev);
+			kfree(wq);
+			goto err_unwind;
+		}
 
 		mutex_init(&wq->wq_lock);
 		init_waitqueue_head(&wq->err_queue);
@@ -220,15 +223,20 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 		wq->enqcmds_retries = IDXD_ENQCMDS_RETRIES;
 		wq->wqcfg = kzalloc_node(idxd->wqcfg_size, GFP_KERNEL, dev_to_node(dev));
 		if (!wq->wqcfg) {
+			put_device(conf_dev);
+			kfree(wq);
 			rc = -ENOMEM;
-			goto err;
+			goto err_unwind;
 		}
 
 		if (idxd->hw.wq_cap.op_config) {
 			wq->opcap_bmap = bitmap_zalloc(IDXD_MAX_OPCAP_BITS, GFP_KERNEL);
 			if (!wq->opcap_bmap) {
+				kfree(wq->wqcfg);
+				put_device(conf_dev);
+				kfree(wq);
 				rc = -ENOMEM;
-				goto err_opcap_bmap;
+				goto err_unwind;
 			}
 			bitmap_copy(wq->opcap_bmap, idxd->opcap_bmap, IDXD_MAX_OPCAP_BITS);
 		}
@@ -239,13 +247,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 
 	return 0;
 
-err_opcap_bmap:
-	kfree(wq->wqcfg);
-
-err:
-	put_device(conf_dev);
-	kfree(wq);
-
+err_unwind:
 	while (--i >= 0) {
 		wq = idxd->wqs[i];
 		if (idxd->hw.wq_cap.op_config)
@@ -254,11 +256,10 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
 		conf_dev = wq_confdev(wq);
 		put_device(conf_dev);
 		kfree(wq);
-
 	}
 	bitmap_free(idxd->wq_enable_map);
 
-err_bitmap:
+err_free_wqs:
 	kfree(idxd->wqs);
 
 	return rc;