[PATCH AUTOSEL 5.4 18/22] pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv

[Sasha Levin]

From: Krishna Kumar <krishnak at linux.ibm.com>

[ Upstream commit 335e35b748527f0c06ded9eebb65387f60647fda ]

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

The crash occurs because although the MSI data structure has been
released during disable/hot-unplug path and it has been assigned
with NULL, still during unregistration the code was again trying to
explicitly disable the MSI which causes the NULL pointer dereference and
kernel crash.

The patch fixes the check during unregistration path to prevent invoking
pci_disable_msi/msix() since its data structure is already freed.

Reported-by: Timothy Pearson <tpearson at raptorengineering.com>
Closes: https://lore.kernel.org/all/1981605666.2142272.1703742465927.JavaMail.zimbra@raptorengineeringinc.com/
Acked-by: Bjorn Helgaas <bhelgaas at google.com>
Tested-by: Shawn Anastasio <sanastasio at raptorengineering.com>
Signed-off-by: Krishna Kumar <krishnak at linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Link: https://msgid.link/20240701074513.94873-2-krishnak@linux.ibm.com
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 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 d7b2b47bc33eb..3824942618305 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -35,7 +35,6 @@ 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) {
@@ -54,7 +53,7 @@ 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)
-- 
2.43.0