[PATCH 1/2] uio: be aware of open(), mmap(), close()

[Benedikt Spranger]

After open(), mmap(), close() the mmaped pointer is valid. Removing the
underlaying module causes a Oops or other strange effects. Keep all structures
valid till the last user is gone.

Signed-off-by: Benedikt Spranger <b.spranger@xxxxxxxxxxxxx>
---
 drivers/uio/uio.c             |   59 ++++++++++++++++++++++++++++++-----------
 drivers/uio/uio_pdrv_genirq.c |    4 +--
 include/linux/uio_driver.h    |    4 +--
 3 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 5110f36..b96499a 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -433,8 +433,22 @@ static irqreturn_t uio_interrupt(int irq, void *dev_id)
 struct uio_listener {
 	struct uio_device *dev;
 	s32 event_count;
+	struct kref kref;
 };
 
+static void uio_release_listener(struct kref *kref)
+{
+	struct uio_listener *listener = container_of(kref, struct uio_listener,
+						     kref);
+	struct uio_device *idev = listener->dev;
+
+	if (idev->info->release)
+		idev->info->release(idev->info);
+
+	module_put(idev->owner);
+	kfree(listener);
+}
+
 static int uio_open(struct inode *inode, struct file *filep)
 {
 	struct uio_device *idev;
@@ -465,10 +479,13 @@ static int uio_open(struct inode *inode, struct file *filep)
 	filep->private_data = listener;
 
 	if (idev->info->open) {
-		ret = idev->info->open(idev->info, inode);
+		ret = idev->info->open(idev->info);
 		if (ret)
 			goto err_infoopen;
 	}
+
+	kref_init(&listener->kref);
+
 	return 0;
 
 err_infoopen:
@@ -491,16 +508,11 @@ static int uio_fasync(int fd, struct file *filep, int on)
 
 static int uio_release(struct inode *inode, struct file *filep)
 {
-	int ret = 0;
 	struct uio_listener *listener = filep->private_data;
-	struct uio_device *idev = listener->dev;
 
-	if (idev->info->release)
-		ret = idev->info->release(idev->info, inode);
+	kref_put(&listener->kref, uio_release_listener);
 
-	module_put(idev->owner);
-	kfree(listener);
-	return ret;
+	return 0;
 }
 
 static unsigned int uio_poll(struct file *filep, poll_table *wait)
@@ -605,19 +617,22 @@ static int uio_find_mem_index(struct vm_area_struct *vma)
 
 static void uio_vma_open(struct vm_area_struct *vma)
 {
-	struct uio_device *idev = vma->vm_private_data;
-	idev->vma_count++;
+	struct uio_listener *listener = vma->vm_private_data;
+
+	kref_get(&listener->kref);
 }
 
 static void uio_vma_close(struct vm_area_struct *vma)
 {
-	struct uio_device *idev = vma->vm_private_data;
-	idev->vma_count--;
+	struct uio_listener *listener = vma->vm_private_data;
+
+	kref_put(&listener->kref, uio_release_listener);
 }
 
 static int uio_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-	struct uio_device *idev = vma->vm_private_data;
+	struct uio_listener *listener = vma->vm_private_data;
+	struct uio_device *idev = listener->dev;
 	struct page *page;
 	unsigned long offset;
 
@@ -646,20 +661,34 @@ static const struct vm_operations_struct uio_vm_ops = {
 	.fault = uio_vma_fault,
 };
 
+static const struct vm_operations_struct uio_phys_ops = {
+	.open = uio_vma_open,
+	.close = uio_vma_close,
+};
+
 static int uio_mmap_physical(struct vm_area_struct *vma)
 {
 	struct uio_device *idev = vma->vm_private_data;
 	int mi = uio_find_mem_index(vma);
+	int ret;
+
 	if (mi < 0)
 		return -EINVAL;
 
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_ops = &uio_phys_ops;
 
-	return remap_pfn_range(vma,
+	ret = remap_pfn_range(vma,
 			       vma->vm_start,
 			       idev->info->mem[mi].addr >> PAGE_SHIFT,
 			       vma->vm_end - vma->vm_start,
 			       vma->vm_page_prot);
+	if (ret)
+		return ret;
+
+	uio_vma_open(vma);
+
+	return 0;
 }
 
 static int uio_mmap_logical(struct vm_area_struct *vma)
@@ -681,7 +710,7 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
 	if (vma->vm_end < vma->vm_start)
 		return -EINVAL;
 
-	vma->vm_private_data = idev;
+	vma->vm_private_data = listener;
 
 	mi = uio_find_mem_index(vma);
 	if (mi < 0)
diff --git a/drivers/uio/uio_pdrv_genirq.c b/drivers/uio/uio_pdrv_genirq.c
index 42202cd..a4e32fa 100644
--- a/drivers/uio/uio_pdrv_genirq.c
+++ b/drivers/uio/uio_pdrv_genirq.c
@@ -37,7 +37,7 @@ struct uio_pdrv_genirq_platdata {
 	struct platform_device *pdev;
 };
 
-static int uio_pdrv_genirq_open(struct uio_info *info, struct inode *inode)
+static int uio_pdrv_genirq_open(struct uio_info *info)
 {
 	struct uio_pdrv_genirq_platdata *priv = info->priv;
 
@@ -46,7 +46,7 @@ static int uio_pdrv_genirq_open(struct uio_info *info, struct inode *inode)
 	return 0;
 }
 
-static int uio_pdrv_genirq_release(struct uio_info *info, struct inode *inode)
+static int uio_pdrv_genirq_release(struct uio_info *info)
 {
 	struct uio_pdrv_genirq_platdata *priv = info->priv;
 
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 1ad4724..1bc6493 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -92,8 +92,8 @@ struct uio_info {
 	void			*priv;
 	irqreturn_t (*handler)(int irq, struct uio_info *dev_info);
 	int (*mmap)(struct uio_info *info, struct vm_area_struct *vma);
-	int (*open)(struct uio_info *info, struct inode *inode);
-	int (*release)(struct uio_info *info, struct inode *inode);
+	int (*open)(struct uio_info *info);
+	void (*release)(struct uio_info *info);
 	int (*irqcontrol)(struct uio_info *info, s32 irq_on);
 };
 
-- 
1.7.10.4

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