pti: double-free security PTI fix

This patch fixes a double-free error that will not always be
seen unless /dev/pti char interface is stressed.

Signed-off-by: J Freyensee <james_p_freyensee@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/misc/pti.c b/drivers/misc/pti.c
index bb6f9255c17c..be4857358d91 100644
--- a/drivers/misc/pti.c
+++ b/drivers/misc/pti.c
@@ -317,7 +317,8 @@ EXPORT_SYMBOL_GPL(pti_request_masterchannel);
  *                              a master, channel ID address
  *                              used to write to PTI HW.
  *
- * @mc: master, channel apeture ID address to be released.
+ * @mc: master, channel apeture ID address to be released.  This
+ *      will de-allocate the structure via kfree().
  */
 void pti_release_masterchannel(struct pti_masterchannel *mc)
 {
@@ -581,7 +582,7 @@ static int pti_char_open(struct inode *inode, struct file *filp)
 static int pti_char_release(struct inode *inode, struct file *filp)
 {
         pti_release_masterchannel(filp->private_data);
-        kfree(filp->private_data);
+        filp->private_data = NULL;
         return 0;
 }