iommu/vt-d: Fix NULL pointer dereference in dev_iommu_priv_set()

The dev_iommu_priv_set() must be called after probe_device(). This fixes
a NULL pointer deference bug when booting a system with kernel cmdline
"intel_iommu=on,igfx_off", where the dev_iommu_priv_set() is abused.

The following stacktrace was produced:

 Command line: BOOT_IMAGE=/isolinux/bzImage console=tty1 intel_iommu=on,igfx_off
 ...
 DMAR: Host address width 39
 DMAR: DRHD base: 0x000000fed90000 flags: 0x0
 DMAR: dmar0: reg_base_addr fed90000 ver 1:0 cap 1c0000c40660462 ecap 19e2ff0505e
 DMAR: DRHD base: 0x000000fed91000 flags: 0x1
 DMAR: dmar1: reg_base_addr fed91000 ver 1:0 cap d2008c40660462 ecap f050da
 DMAR: RMRR base: 0x0000009aa9f000 end: 0x0000009aabefff
 DMAR: RMRR base: 0x0000009d000000 end: 0x0000009f7fffff
 DMAR: No ATSR found
 BUG: kernel NULL pointer dereference, address: 0000000000000038
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 0 P4D 0
 Oops: 0002 [#1] SMP PTI
 CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.9.0-devel+ #2
 Hardware name: LENOVO 20HGS0TW00/20HGS0TW00, BIOS N1WET46S (1.25s ) 03/30/2018
 RIP: 0010:intel_iommu_init+0xed0/0x1136
 Code: fe e9 61 02 00 00 bb f4 ff ff ff e9 57 02 00 00 48 63 d1 48 c1 e2 04 48
       03 50 20 48 8b 12 48 85 d2 74 0b 48 8b 92 d0 02 00 00 48 89 7a 38 ff c1
       e9 15 f5 ff ff 48 c7 c7 60 99 ac a7 49 c7 c7 a0
 RSP: 0000:ffff96d180073dd0 EFLAGS: 00010282
 RAX: ffff8c91037a7d20 RBX: 0000000000000000 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff
 RBP: ffff96d180073e90 R08: 0000000000000001 R09: ffff8c91039fe3c0
 R10: 0000000000000226 R11: 0000000000000226 R12: 000000000000000b
 R13: ffff8c910367c650 R14: ffffffffa8426d60 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff8c9107480000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000038 CR3: 00000004b100a001 CR4: 00000000003706e0
 Call Trace:
  ? _raw_spin_unlock_irqrestore+0x1f/0x30
  ? call_rcu+0x10e/0x320
  ? trace_hardirqs_on+0x2c/0xd0
  ? rdinit_setup+0x2c/0x2c
  ? e820__memblock_setup+0x8b/0x8b
  pci_iommu_init+0x16/0x3f
  do_one_initcall+0x46/0x1e4
  kernel_init_freeable+0x169/0x1b2
  ? rest_init+0x9f/0x9f
  kernel_init+0xa/0x101
  ret_from_fork+0x22/0x30
 Modules linked in:
 CR2: 0000000000000038
 ---[ end trace 3653722a6f936f18 ]---

Fixes: 01b9d4e2 ("iommu/vt-d: Use dev_iommu_priv_get/set()")
Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Reported-by: Wendy Wang <wendy.wang@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Link: https://lore.kernel.org/linux-iommu/96717683-70be-7388-3d2f-61131070a96a@secunet.com/
Link: https://lore.kernel.org/r/20200903065132.16879-1-baolu.lu@linux.intel.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel/iommu.c

@@ -364,7 +364,6 @@ static int iommu_skip_te_disable;
 int intel_iommu_gfx_mapped;
 EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
 
-#define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1))
 #define DEFER_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-2))
 struct device_domain_info *get_domain_info(struct device *dev)
 {
@@ -374,8 +373,7 @@ struct device_domain_info *get_domain_info(struct device *dev)
 		return NULL;
 
 	info = dev_iommu_priv_get(dev);
-	if (unlikely(info == DUMMY_DEVICE_DOMAIN_INFO ||
-		     info == DEFER_DEVICE_DOMAIN_INFO))
+	if (unlikely(info == DEFER_DEVICE_DOMAIN_INFO))
 		return NULL;
 
 	return info;
@@ -742,11 +740,6 @@ struct context_entry *iommu_context_addr(struct intel_iommu *iommu, u8 bus,
 	return &context[devfn];
 }
 
-static int iommu_dummy(struct device *dev)
-{
-	return dev_iommu_priv_get(dev) == DUMMY_DEVICE_DOMAIN_INFO;
-}
-
 static bool attach_deferred(struct device *dev)
 {
 	return dev_iommu_priv_get(dev) == DEFER_DEVICE_DOMAIN_INFO;
@@ -779,6 +772,53 @@ is_downstream_to_pci_bridge(struct device *dev, struct device *bridge)
 	return false;
 }
 
+static bool quirk_ioat_snb_local_iommu(struct pci_dev *pdev)
+{
+	struct dmar_drhd_unit *drhd;
+	u32 vtbar;
+	int rc;
+
+	/* We know that this device on this chipset has its own IOMMU.
+	 * If we find it under a different IOMMU, then the BIOS is lying
+	 * to us. Hope that the IOMMU for this device is actually
+	 * disabled, and it needs no translation...
+	 */
+	rc = pci_bus_read_config_dword(pdev->bus, PCI_DEVFN(0, 0), 0xb0, &vtbar);
+	if (rc) {
+		/* "can't" happen */
+		dev_info(&pdev->dev, "failed to run vt-d quirk\n");
+		return false;
+	}
+	vtbar &= 0xffff0000;
+
+	/* we know that the this iommu should be at offset 0xa000 from vtbar */
+	drhd = dmar_find_matched_drhd_unit(pdev);
+	if (!drhd || drhd->reg_base_addr - vtbar != 0xa000) {
+		pr_warn_once(FW_BUG "BIOS assigned incorrect VT-d unit for Intel(R) QuickData Technology device\n");
+		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+		return true;
+	}
+
+	return false;
+}
+
+static bool iommu_is_dummy(struct intel_iommu *iommu, struct device *dev)
+{
+	if (!iommu || iommu->drhd->ignored)
+		return true;
+
+	if (dev_is_pci(dev)) {
+		struct pci_dev *pdev = to_pci_dev(dev);
+
+		if (pdev->vendor == PCI_VENDOR_ID_INTEL &&
+		    pdev->device == PCI_DEVICE_ID_INTEL_IOAT_SNB &&
+		    quirk_ioat_snb_local_iommu(pdev))
+			return true;
+	}
+
+	return false;
+}
+
 struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 {
 	struct dmar_drhd_unit *drhd = NULL;
@@ -788,7 +828,7 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 	u16 segment = 0;
 	int i;
 
-	if (!dev || iommu_dummy(dev))
+	if (!dev)
 		return NULL;
 
 	if (dev_is_pci(dev)) {
@@ -805,7 +845,7 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 		dev = &ACPI_COMPANION(dev)->dev;
 
 	rcu_read_lock();
-	for_each_active_iommu(iommu, drhd) {
+	for_each_iommu(iommu, drhd) {
 		if (pdev && segment != drhd->segment)
 			continue;
 
@@ -841,6 +881,9 @@ struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 	}
 	iommu = NULL;
  out:
+	if (iommu_is_dummy(iommu, dev))
+		iommu = NULL;
+
 	rcu_read_unlock();
 
 	return iommu;
@@ -2447,7 +2490,7 @@ struct dmar_domain *find_domain(struct device *dev)
 {
 	struct device_domain_info *info;
 
-	if (unlikely(attach_deferred(dev) || iommu_dummy(dev)))
+	if (unlikely(attach_deferred(dev)))
 		return NULL;
 
 	/* No lock here, assumes no domain exit in normal case */
@@ -3989,35 +4032,6 @@ static void __init iommu_exit_mempool(void)
 	iova_cache_put();
 }
 
-static void quirk_ioat_snb_local_iommu(struct pci_dev *pdev)
-{
-	struct dmar_drhd_unit *drhd;
-	u32 vtbar;
-	int rc;
-
-	/* We know that this device on this chipset has its own IOMMU.
-	 * If we find it under a different IOMMU, then the BIOS is lying
-	 * to us. Hope that the IOMMU for this device is actually
-	 * disabled, and it needs no translation...
-	 */
-	rc = pci_bus_read_config_dword(pdev->bus, PCI_DEVFN(0, 0), 0xb0, &vtbar);
-	if (rc) {
-		/* "can't" happen */
-		dev_info(&pdev->dev, "failed to run vt-d quirk\n");
-		return;
-	}
-	vtbar &= 0xffff0000;
-
-	/* we know that the this iommu should be at offset 0xa000 from vtbar */
-	drhd = dmar_find_matched_drhd_unit(pdev);
-	if (!drhd || drhd->reg_base_addr - vtbar != 0xa000) {
-		pr_warn_once(FW_BUG "BIOS assigned incorrect VT-d unit for Intel(R) QuickData Technology device\n");
-		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
-		dev_iommu_priv_set(&pdev->dev, DUMMY_DEVICE_DOMAIN_INFO);
-	}
-}
-DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IOAT_SNB, quirk_ioat_snb_local_iommu);
-
 static void __init init_no_remapping_devices(void)
 {
 	struct dmar_drhd_unit *drhd;
@@ -4049,12 +4063,8 @@ static void __init init_no_remapping_devices(void)
 		/* This IOMMU has *only* gfx devices. Either bypass it or
 		   set the gfx_mapped flag, as appropriate */
 		drhd->gfx_dedicated = 1;
-		if (!dmar_map_gfx) {
+		if (!dmar_map_gfx)
 			drhd->ignored = 1;
-			for_each_active_dev_scope(drhd->devices,
-						  drhd->devices_cnt, i, dev)
-				dev_iommu_priv_set(dev, DUMMY_DEVICE_DOMAIN_INFO);
-		}
 	}
 }