linux-kernel - [PATCH 1/4] UIO: hold a reference to the device's owner while the device is open

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Message-Id: <1207831023-8583-2-git-send-email-Uwe.Kleine-Koenig@digi.com>
Date:	Thu, 10 Apr 2008 14:37:00 +0200
From:	Uwe Kleine-König <Uwe.Kleine-Koenig@...i.com>
To:	"Hans J. Koch" <hjk@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] UIO: hold a reference to the device's owner while the device is open

Otherwise the device might just disappear while /dev/uioX is being used
which results in an Oops.

Signed-off-by: Uwe Kleine-König <Uwe.Kleine-Koenig@...i.com>
---
 drivers/uio/uio.c |   40 +++++++++++++++++++++++-----------------
 1 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 1175908..005fc55 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -301,25 +301,35 @@ static int uio_open(struct inode *inode, struct file *filep)
 	if (!idev)
 		return -ENODEV;
 
+	if (!try_module_get(idev->owner)) {
+		ret = -ENODEV;
+		goto err_module_get;
+	}
+
 	listener = kmalloc(sizeof(*listener), GFP_KERNEL);
-	if (!listener)
-		return -ENOMEM;
+	if (!listener) {
+		ret = -ENOMEM;
+		goto err_alloc_listener;
+	}
 
 	listener->dev = idev;
 	listener->event_count = atomic_read(&idev->event);
 	filep->private_data = listener;
 
 	if (idev->info->open) {
-		if (!try_module_get(idev->owner))
-			return -ENODEV;
 		ret = idev->info->open(idev->info, inode);
-		module_put(idev->owner);
-	}
+		if (ret) {
+			kfree(listener);
+err_alloc_listener:
 
-	if (ret)
-		kfree(listener);
+			module_put(idev->owner);
+err_module_get:
 
-	return ret;
+			return ret;
+		}
+	}
+
+	return 0;
 }
 
 static int uio_fasync(int fd, struct file *filep, int on)
@@ -336,12 +346,11 @@ static int uio_release(struct inode *inode, struct file *filep)
 	struct uio_listener *listener = filep->private_data;
 	struct uio_device *idev = listener->dev;
 
-	if (idev->info->release) {
-		if (!try_module_get(idev->owner))
-			return -ENODEV;
+	if (idev->info->release)
 		ret = idev->info->release(idev->info, inode);
-		module_put(idev->owner);
-	}
+
+	module_put(idev->owner);
+
 	if (filep->f_flags & FASYNC)
 		ret = uio_fasync(-1, filep, 0);
 	kfree(listener);
@@ -510,10 +519,7 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
 		return -EINVAL;
 
 	if (idev->info->mmap) {
-		if (!try_module_get(idev->owner))
-			return -ENODEV;
 		ret = idev->info->mmap(idev->info, vma);
-		module_put(idev->owner);
 		return ret;
 	}
 
-- 
1.5.4.5

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