linux-kernel - [PATCH 3.16 039/192] NFC: fix broken device allocation

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Message-ID: <lsq.1507553064.602766572@decadent.org.uk>
Date:   Mon, 09 Oct 2017 13:44:24 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Samuel Ortiz" <sameo@...ux.intel.com>,
        "Johan Hovold" <johan@...nel.org>
Subject: [PATCH 3.16 039/192] NFC: fix broken device allocation

3.16.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@...nel.org>

commit 20777bc57c346b6994f465e0d8261a7fbf213a09 upstream.

Commit 7eda8b8e9677 ("NFC: Use IDR library to assing NFC devices IDs")
moved device-id allocation and struct-device initialisation from
nfc_allocate_device() to nfc_register_device().

This broke just about every nfc-device-registration error path, which
continue to call nfc_free_device() that tries to put the device
reference of the now uninitialised (but zeroed) struct device:

kobject: '(null)' (ce316420): is not initialized, yet kobject_put() is being called.

The late struct-device initialisation also meant that various work
queues whose names are derived from the nfc device name were also
misnamed:

  421 root         0 SW<  [(null)_nci_cmd_]
  422 root         0 SW<  [(null)_nci_rx_w]
  423 root         0 SW<  [(null)_nci_tx_w]

Move the id-allocation and struct-device initialisation back to
nfc_allocate_device() and fix up the single call site which did not use
nfc_free_device() in its error path.

Fixes: 7eda8b8e9677 ("NFC: Use IDR library to assing NFC devices IDs")
Cc: Samuel Ortiz <sameo@...ux.intel.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Samuel Ortiz <sameo@...ux.intel.com>
[bwh: Backported to 3.16: drop change in nci_allocate_device()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -950,6 +950,8 @@ static void nfc_release(struct device *d
 			kfree(se);
 	}
 
+	ida_simple_remove(&nfc_index_ida, dev->idx);
+
 	kfree(dev);
 }
 
@@ -1024,6 +1026,7 @@ struct nfc_dev *nfc_allocate_device(stru
 				    int tx_headroom, int tx_tailroom)
 {
 	struct nfc_dev *dev;
+	int rc;
 
 	if (!ops->start_poll || !ops->stop_poll || !ops->activate_target ||
 	    !ops->deactivate_target || !ops->im_transceive)
@@ -1036,6 +1039,15 @@ struct nfc_dev *nfc_allocate_device(stru
 	if (!dev)
 		return NULL;
 
+	rc = ida_simple_get(&nfc_index_ida, 0, 0, GFP_KERNEL);
+	if (rc < 0)
+		goto err_free_dev;
+	dev->idx = rc;
+
+	dev->dev.class = &nfc_class;
+	dev_set_name(&dev->dev, "nfc%d", dev->idx);
+	device_initialize(&dev->dev);
+
 	dev->ops = ops;
 	dev->supported_protocols = supported_protocols;
 	dev->tx_headroom = tx_headroom;
@@ -1058,6 +1070,11 @@ struct nfc_dev *nfc_allocate_device(stru
 	}
 
 	return dev;
+
+err_free_dev:
+	kfree(dev);
+
+	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL(nfc_allocate_device);
 
@@ -1072,14 +1089,6 @@ int nfc_register_device(struct nfc_dev *
 
 	pr_debug("dev_name=%s\n", dev_name(&dev->dev));
 
-	dev->idx = ida_simple_get(&nfc_index_ida, 0, 0, GFP_KERNEL);
-	if (dev->idx < 0)
-		return dev->idx;
-
-	dev->dev.class = &nfc_class;
-	dev_set_name(&dev->dev, "nfc%d", dev->idx);
-	device_initialize(&dev->dev);
-
 	mutex_lock(&nfc_devlist_mutex);
 	nfc_devlist_generation++;
 	rc = device_add(&dev->dev);
@@ -1117,12 +1126,10 @@ EXPORT_SYMBOL(nfc_register_device);
  */
 void nfc_unregister_device(struct nfc_dev *dev)
 {
-	int rc, id;
+	int rc;
 
 	pr_debug("dev_name=%s\n", dev_name(&dev->dev));
 
-	id = dev->idx;
-
 	if (dev->rfkill) {
 		rfkill_unregister(dev->rfkill);
 		rfkill_destroy(dev->rfkill);
@@ -1147,8 +1154,6 @@ void nfc_unregister_device(struct nfc_de
 	nfc_devlist_generation++;
 	device_del(&dev->dev);
 	mutex_unlock(&nfc_devlist_mutex);
-
-	ida_simple_remove(&nfc_index_ida, id);
 }
 EXPORT_SYMBOL(nfc_unregister_device);