dmaengine: idxd: check return result from check_vma() in cdev

The returned result from the check_vma() function in the cdev ->mmap() call
needs to be handled. Add the check and returning error.

Fixes: 42d279f9 ("dmaengine: idxd: add char driver to expose submission portal to userland")
Reported-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/158264926659.9387.14325163515683047959.stgit@djiang5-desk3.ch.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/cdev.c

@@ -137,6 +137,8 @@ static int idxd_cdev_mmap(struct file *filp, struct vm_area_struct *vma)
 
 	dev_dbg(&pdev->dev, "%s called\n", __func__);
 	rc = check_vma(wq, vma, __func__);
+	if (rc < 0)
+		return rc;
 
 	vma->vm_flags |= VM_DONTCOPY;
 	pfn = (base + idxd_get_wq_portal_full_offset(wq->id,