uacce: vma_close clears q->qfrs when freeing qfrs

vma_close frees qfrs but not clears q->qfrs, which still points
to the freed object, leading to subsequent mmap fail.
So vma_close clears q->qfrs as well.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Link: https://lore.kernel.org/r/20230511095921.9331-3-zhangfei.gao@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/uacce/uacce.c

@@ -200,12 +200,15 @@ static int uacce_fops_release(struct inode *inode, struct file *filep)
 static void uacce_vma_close(struct vm_area_struct *vma)
 {
 	struct uacce_queue *q = vma->vm_private_data;
-	struct uacce_qfile_region *qfr = NULL;
 
-	if (vma->vm_pgoff < UACCE_MAX_REGION)
-		qfr = q->qfrs[vma->vm_pgoff];
+	if (vma->vm_pgoff < UACCE_MAX_REGION) {
+		struct uacce_qfile_region *qfr = q->qfrs[vma->vm_pgoff];
 
-	kfree(qfr);
+		mutex_lock(&q->mutex);
+		q->qfrs[vma->vm_pgoff] = NULL;
+		mutex_unlock(&q->mutex);
+		kfree(qfr);
+	}
 }
 
 static const struct vm_operations_struct uacce_vm_ops = {