linux-kernel - Re: [PATCH] driver core: fix race with userland in device

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Date:	Wed, 08 Oct 2014 11:31:54 +0400
From:	Sergey Klyaus <Sergey.Klyaus@...e-it.ru>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver core: fix race with userland in device_add()

bus_add_device() should be called before devtmpfs_create_node(), so when 
userland application opens device from devtmpfs, it wouldn't get ENODEV 
from kernel, because device_add() wasn't completed.

Signed-off-by: Sergey Klyaus <Sergey.Klyaus@...e-IT.Ru>
---
 drivers/base/core.c | 40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 20da3ad..88ee96a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1019,18 +1019,6 @@ int device_add(struct device *dev)
 	if (error)
 		goto attrError;
 
-	if (MAJOR(dev->devt)) {
-		error = device_create_file(dev, &dev_attr_dev);
-		if (error)
-			goto ueventattrError;
-
-		error = device_create_sys_dev_entry(dev);
-		if (error)
-			goto devtattrError;
-
-		devtmpfs_create_node(dev);
-	}
-
 	error = device_add_class_symlinks(dev);
 	if (error)
 		goto SymlinkError;
@@ -1044,7 +1032,19 @@ int device_add(struct device *dev)
 	if (error)
 		goto DPMError;
 	device_pm_add(dev);
-
+	
+	if (MAJOR(dev->devt)) {
+		error = device_create_file(dev, &dev_attr_dev);
+		if (error)
+			goto DevAttrError;
+		
+		error = device_create_sys_dev_entry(dev);
+		if (error)
+			goto SysEntryError;
+		
+		devtmpfs_create_node(dev);
+	}
+	
 	/* Notify clients of device addition.  This call must come
 	 * after dpm_sysfs_add() and before kobject_uevent().
 	 */
@@ -1074,6 +1074,12 @@ int device_add(struct device *dev)
 done:
 	put_device(dev);
 	return error;
+ SysEntryError:
+	if (MAJOR(dev->devt))
+		device_remove_file(dev, &dev_attr_dev);
+ DevAttrError:
+	device_pm_remove(dev);
+	dpm_sysfs_remove(dev);
  DPMError:
 	bus_remove_device(dev);
  BusError:
@@ -1081,14 +1087,6 @@ done:
  AttrsError:
 	device_remove_class_symlinks(dev);
  SymlinkError:
-	if (MAJOR(dev->devt))
-		devtmpfs_delete_node(dev);
-	if (MAJOR(dev->devt))
-		device_remove_sys_dev_entry(dev);
- devtattrError:
-	if (MAJOR(dev->devt))
-		device_remove_file(dev, &dev_attr_dev);
- ueventattrError:
 	device_remove_file(dev, &dev_attr_uevent);
  attrError:
 	kobject_uevent(&dev->kobj, KOBJ_REMOVE);
-- 
1.8.4.5
--
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