iommu/vt-d: Fix crash on boot when DMAR is disabled

andy-shev · joergroedel · commit c37a01779b39 · 2017-02-22T12:25:31.000+01:00
By default CONFIG_INTEL_IOMMU_DEFAULT_ON is not set and thus dmar_disabled variable is set. Intel IOMMU driver based on above doesn't set intel_iommu_enabled variable. The commit b0119e8 ("iommu: Introduce new 'struct iommu_device'") mistakenly assumes it never happens and tries to unregister not ever registered resources, which crashes the kernel at boot time: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: iommu_device_unregister+0x31/0x60 Make unregister procedure conditional in free_iommu(). Fixes: b0119e8 ("iommu: Introduce new 'struct iommu_device'") Cc: Joerg Roedel <jroedel@suse.de> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
@@ -1108,8 +1108,10 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
 static void free_iommu(struct intel_iommu *iommu)
 {
-	iommu_device_sysfs_remove(&iommu->iommu);
-	iommu_device_unregister(&iommu->iommu);
+	if (intel_iommu_enabled) {
+		iommu_device_unregister(&iommu->iommu);
+		iommu_device_sysfs_remove(&iommu->iommu);
+	}
 
 	if (iommu->irq) {
 		if (iommu->pr_irq) {
