[PATCH v2] iommu/amd: Check if domain is NULL in get_domain() and return -EBUSY

[Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

In get_domain(), 'domain' could be NULL before it's passed to dma_ops_domain()
to dereference. And the current code calling get_domain() can't deal with the
returned 'domain' well if its value is NULL.

So before dma_ops_domain() calling, check if 'domain' is NULL, If yes just return
ERR_PTR(-EBUSY) directly.

Reported-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Fixes: df3f7a6e8e85 ('iommu/amd: Use is_attach_deferred call-back')
Signed-off-by: Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/iommu/amd_iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 16f1e6af00b0..2d7d04472555 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2262,6 +2262,9 @@ static struct protection_domain *get_domain(struct device *dev)
 		domain = to_pdomain(io_domain);
 		attach_device(dev, domain);
 	}
+	if (domain == NULL)
+		return ERR_PTR(-EBUSY);
+
 	if (!dma_ops_domain(domain))
 		return ERR_PTR(-EBUSY);
 
-- 
2.5.5