PCI: Add missing bridge lock to pci_bus_lock()

JIRA: https://issues.redhat.com/browse/RHEL-59331
CVE: CVE-2024-46750

commit a4e7728
Author: Dan Williams <dan.j.williams@intel.com>
Date:   Thu May 30 18:04:35 2024 -0700

    PCI: Add missing bridge lock to pci_bus_lock()

    One of the true positives that the cfg_access_lock lockdep effort
    identified is this sequence:

      WARNING: CPU: 14 PID: 1 at drivers/pci/pci.c:4886 pci_bridge_secondary_bus_reset+0x5d/0x70
      RIP: 0010:pci_bridge_secondary_bus_reset+0x5d/0x70
      Call Trace:
       <TASK>
       ? __warn+0x8c/0x190
       ? pci_bridge_secondary_bus_reset+0x5d/0x70
       ? report_bug+0x1f8/0x200
       ? handle_bug+0x3c/0x70
       ? exc_invalid_op+0x18/0x70
       ? asm_exc_invalid_op+0x1a/0x20
       ? pci_bridge_secondary_bus_reset+0x5d/0x70
       pci_reset_bus+0x1d8/0x270
       vmd_probe+0x778/0xa10
       pci_device_probe+0x95/0x120

    Where pci_reset_bus() users are triggering unlocked secondary bus resets.
    Ironically pci_bus_reset(), several calls down from pci_reset_bus(), uses
    pci_bus_lock() before issuing the reset which locks everything *but* the
    bridge itself.

    For the same motivation as adding:

      bridge = pci_upstream_bridge(dev);
      if (bridge)
        pci_dev_lock(bridge);

    to pci_reset_function() for the "bus" and "cxl_bus" reset cases, add
    pci_dev_lock() for @bus->self to pci_bus_lock().

    Link: https://lore.kernel.org/r/171711747501.1628941.15217746952476635316.stgit@dwillia2-xfh.jf.intel.com
    Reported-by: Imre Deak <imre.deak@intel.com>
    Closes: http://lore.kernel.org/r/6657833b3b5ae_14984b29437@dwillia2-xfh.jf.intel.com.notmuch
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Signed-off-by: Keith Busch <kbusch@kernel.org>
    [bhelgaas: squash in recursive locking deadlock fix from Keith Busch:
    https://lore.kernel.org/r/20240711193650.701834-1-kbusch@meta.com]
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    Tested-by: Hans de Goede <hdegoede@redhat.com>
    Tested-by: Kalle Valo <kvalo@kernel.org>
    Reviewed-by: Dave Jiang <dave.jiang@intel.com>

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

Author: CKI Backport Bot

drivers/pci/pci.c

@@ -5360,10 +5360,12 @@ static void pci_bus_lock(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 
+	pci_dev_lock(bus->self);
 	list_for_each_entry(dev, &bus->devices, bus_list) {
-		pci_dev_lock(dev);
 		if (dev->subordinate)
 			pci_bus_lock(dev->subordinate);
+		else
+			pci_dev_lock(dev);
 	}
 }
 
@@ -5375,33 +5377,37 @@ static void pci_bus_unlock(struct pci_bus *bus)
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
-		pci_dev_unlock(dev);
+		else
+			pci_dev_unlock(dev);
 	}
+	pci_dev_unlock(bus->self);
 }
 
 /* Return 1 on successful lock, 0 on contention */
 static int pci_bus_trylock(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 
+	if (!pci_dev_trylock(bus->self))
+		return 0;
+
 	list_for_each_entry(dev, &bus->devices, bus_list) {
-		if (!pci_dev_trylock(dev))
-			goto unlock;
 		if (dev->subordinate) {
-			if (!pci_bus_trylock(dev->subordinate)) {
-				pci_dev_unlock(dev);
+			if (!pci_bus_trylock(dev->subordinate))
 				goto unlock;
-			}
-		}
+		} else if (!pci_dev_trylock(dev))
+			goto unlock;
 	}
 	return 1;
 
 unlock:
 	list_for_each_entry_continue_reverse(dev, &bus->devices, bus_list) {
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
-		pci_dev_unlock(dev);
+		else
+			pci_dev_unlock(dev);
 	}
+	pci_dev_unlock(bus->self);
 	return 0;
 }
 
@@ -5433,9 +5439,10 @@ static void pci_slot_lock(struct pci_slot *slot)
 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
 		if (!dev->slot || dev->slot != slot)
 			continue;
-		pci_dev_lock(dev);
 		if (dev->subordinate)
 			pci_bus_lock(dev->subordinate);
+		else
+			pci_dev_lock(dev);
 	}
 }
 
@@ -5461,14 +5468,13 @@ static int pci_slot_trylock(struct pci_slot *slot)
 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
 		if (!dev->slot || dev->slot != slot)
 			continue;
-		if (!pci_dev_trylock(dev))
-			goto unlock;
 		if (dev->subordinate) {
 			if (!pci_bus_trylock(dev->subordinate)) {
 				pci_dev_unlock(dev);
 				goto unlock;
 			}
-		}
+		} else if (!pci_dev_trylock(dev))
+			goto unlock;
 	}
 	return 1;
 
@@ -5479,7 +5485,8 @@ static int pci_slot_trylock(struct pci_slot *slot)
 			continue;
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
-		pci_dev_unlock(dev);
+		else
+			pci_dev_unlock(dev);
 	}
 	return 0;
 }