linux-kernel - [PATCH v3 1/2] pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv

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Date: Mon, 24 Jun 2024 17:39:27 +0530
From: Krishna Kumar <krishnak@...ux.ibm.com>
To: mpe@...erman.id.au, npiggin@...il.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, brking@...ux.vnet.ibm.com,
        gbatra@...ux.ibm.com, aneesh.kumar@...nel.org,
        christophe.leroy@...roup.eu, nathanl@...ux.ibm.com,
        bhelgaas@...gle.com, oohall@...il.com, tpearson@...torengineering.com,
        mahesh.salgaonkar@...ibm.com, Krishna Kumar <krishnak@...ux.ibm.com>
Subject: [PATCH v3 1/2] pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv

Description of the problem: The hotplug driver for powerpc
(pci/hotplug/pnv_php.c) gives kernel crash when we try to
hot-unplug/disable the PCIe switch/bridge from the PHB.

Root Cause of Crash: The crash is due to the reason that, though the msi
data structure has been released during disable/hot-unplug path and it
has been assigned with NULL, still during unregistartion the code was
again trying to explicitly disable the msi which causes the Null pointer
dereference and kernel crash.

Proposed Fix : The fix is to correct the check during unregistration path
so that the code should not  try to invoke pci_disable_msi/msix() if its
data structure is already freed.

Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Gaurav Batra <gbatra@...ux.ibm.com>
Cc: Nathan Lynch <nathanl@...ux.ibm.com>
Cc: Brian King <brking@...ux.vnet.ibm.com>

Signed-off-by: Krishna Kumar <krishnak@...ux.ibm.com>
---
 drivers/pci/hotplug/pnv_php.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index 694349be9d0a..573a41869c15 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -40,7 +40,6 @@ static void pnv_php_disable_irq(struct pnv_php_slot *php_slot,
 				bool disable_device)
 {
 	struct pci_dev *pdev = php_slot->pdev;
-	int irq = php_slot->irq;
 	u16 ctrl;
 
 	if (php_slot->irq > 0) {
@@ -59,7 +58,7 @@ static void pnv_php_disable_irq(struct pnv_php_slot *php_slot,
 		php_slot->wq = NULL;
 	}
 
-	if (disable_device || irq > 0) {
+	if (disable_device) {
 		if (pdev->msix_enabled)
 			pci_disable_msix(pdev);
 		else if (pdev->msi_enabled)
-- 
2.45.0