IB/hfi1: Do not free hfi1 cdev parent structure early

The deletion of a cdev is not a fence for holding off references to the
structure. The driver attempts to delete the cdev and then proceeds to
free the parent structure, the hfi1_devdata, or dd. This can potentially
lead to a kernel panic in situations where a user has an FD for the cdev
open, and the pci device gets removed. If the user then closes the FD
there will be a NULL dereference when trying to do put on the cdev's
kobject.

Fix this by pointing the cdev's kobject.parent at a new kobject embedded
in its parent structure. Also take a reference when the device is opened
and put it back when it is closed.

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/staging/rdma/hfi1/device.c b/drivers/staging/rdma/hfi1/device.c
index 6ee800f0359f..bf64b5a7bfd7 100644
--- a/drivers/staging/rdma/hfi1/device.c
+++ b/drivers/staging/rdma/hfi1/device.c
@@ -60,7 +60,8 @@ static dev_t hfi1_dev;
 int hfi1_cdev_init(int minor, const char *name,
 		   const struct file_operations *fops,
 		   struct cdev *cdev, struct device **devp,
-		   bool user_accessible)
+		   bool user_accessible,
+		   struct kobject *parent)
 {
 	const dev_t dev = MKDEV(MAJOR(hfi1_dev), minor);
 	struct device *device = NULL;
@@ -68,6 +69,7 @@ int hfi1_cdev_init(int minor, const char *name,
 
 	cdev_init(cdev, fops);
 	cdev->owner = THIS_MODULE;
+	cdev->kobj.parent = parent;
 	kobject_set_name(&cdev->kobj, name);
 
 	ret = cdev_add(cdev, dev, 1);