[xen master] IOMMU: make domctl handler tolerate NULL domain

[patchbot@xxxxxxx]

commit fa4d84e6dd3c3bfd23a525b75a5483d4ce15adbb
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Apr 26 10:25:54 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Apr 26 10:25:54 2022 +0200

    IOMMU: make domctl handler tolerate NULL domain
    
    Besides the reporter's issue of hitting a NULL deref when !CONFIG_GDBSX,
    XEN_DOMCTL_test_assign_device can legitimately end up having NULL passed
    here, when the domctl was passed DOMID_INVALID.
    
    Fixes: 71e617a6b8f6 ("use is_iommu_enabled() where appropriate...")
    Reported-by: Cheyenne Wills <cheyenne.wills@xxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
    Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/drivers/passthrough/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 1109a86532..67ffe6635e 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -568,7 +568,7 @@ int iommu_do_domctl(
 {
     int ret = -ENODEV;
 
-    if ( !is_iommu_enabled(d) )
+    if ( !(d ? is_iommu_enabled(d) : iommu_enabled) )
         return -EOPNOTSUPP;
 
 #ifdef CONFIG_HAS_PCI
--
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