pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv

[ 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@raptorengineering.com>
Closes: https://lore.kernel.org/all/1981605666.2142272.1703742465927.JavaMail.zimbra@raptorengineeringinc.com/
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Signed-off-by: Krishna Kumar <krishnak@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240701074513.94873-2-krishnak@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index 04565162a44954dbf97f5bd77b12c68f200586aa..cf9c0e75f0be483d665b108dc9c0fefafd044fa7 100644 (file)
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -38,7 +38,6 @@ 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) {
@@ -57,7 +56,7 @@ 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)