Re: [PATCH v3 1/2] powerpc/eeh: Avoid use after free in eeh_handle_special_event()

---
V2: check a specific return path instead of looking at the PE itself
V3: use a bool instead of a non-specific int return
---
 arch/powerpc/kernel/eeh_driver.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index b94887165a10..e50d1470714f 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c

@@ -724,7 +724,7 @@ static int eeh_reset_device(struct eeh_pe *pe, struct pci_bus *bus,
  */
 #define MAX_WAIT_FOR_RECOVERY 300

-static void eeh_handle_normal_event(struct eeh_pe *pe)
+static bool eeh_handle_normal_event(struct eeh_pe *pe)
 {
 	struct pci_bus *frozen_bus;
 	struct eeh_dev *edev, *tmp;

@@ -736,7 +736,7 @@ static void eeh_handle_normal_event(struct eeh_pe *pe)
 	if (!frozen_bus) {
 		pr_err("%s: Cannot find PCI bus for PHB#%x-PE#%x\n",
 			__func__, pe->phb->global_number, pe->addr);
-		return;
+		return false;
 	}

 	eeh_pe_update_time_stamp(pe);

@@ -870,7 +870,7 @@ static void eeh_handle_normal_event(struct eeh_pe *pe)
 	pr_info("EEH: Notify device driver to resume\n");
 	eeh_pe_dev_traverse(pe, eeh_report_resume, NULL);

-	return;
+	return false;

 excess_failures:
 	/*

@@ -915,8 +915,12 @@ static void eeh_handle_normal_event(struct eeh_pe *pe)
 			pci_lock_rescan_remove();
 			pci_hp_remove_devices(frozen_bus);
 			pci_unlock_rescan_remove();
+
+			/* The passed PE should no longer be used */
+			return true;
 		}
 	}
+	return false;
 }

 static void eeh_handle_special_event(void)

@@ -982,7 +986,14 @@ static void eeh_handle_special_event(void)
 		 */
 		if (rc == EEH_NEXT_ERR_FROZEN_PE ||
 		    rc == EEH_NEXT_ERR_FENCED_PHB) {
-			eeh_handle_normal_event(pe);
+			/*
+			 * eeh_handle_normal_event() can make the PE stale if it
+			 * determines that the PE cannot possibly be recovered.
+			 * Don't modify the PE state if that's the case.
+			 */
+			if (eeh_handle_normal_event(pe))
+				continue;
+
 			eeh_pe_state_clear(pe, EEH_PE_RECOVERING);
 		} else {
 			pci_lock_rescan_remove();