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

JIRA: https://issues.redhat.com/browse/RHEL-59436
CVE: CVE-2024-46761

commit 335e35b
Author: Krishna Kumar <krishnak@linux.ibm.com>
Date:   Mon Jul 1 13:15:06 2024 +0530

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

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

Author: CKI Backport Bot

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)