s390/pci: Fix stale function handles in error handling

JIRA: https://issues.redhat.com/browse/RHEL-105598

commit 4553792
Author: Niklas Schnelle <schnelle@linux.ibm.com>
Date:   Wed Jun 25 11:28:28 2025 +0200

    s390/pci: Fix stale function handles in error handling

    The error event information for PCI error events contains a function
    handle for the respective function. This handle is generally captured at
    the time the error event was recorded. Due to delays in processing or
    cascading issues, it may happen that during firmware recovery multiple
    events are generated. When processing these events in order Linux may
    already have recovered an affected function making the event information
    stale. Fix this by doing an unconditional CLP List PCI function
    retrieving the current function handle with the zdev->state_lock held
    and ignoring the event if its function handle is stale.

    Cc: stable@vger.kernel.org
    Fixes: 4cdf2f4 ("s390/pci: implement minimal PCI error recovery")
    Reviewed-by: Julian Ruess <julianr@linux.ibm.com>
    Reviewed-by: Gerd Bayer <gbayer@linux.ibm.com>
    Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
    Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
    Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Mete Durlu <mdurlu@redhat.com>

Author: Mete Durlu

arch/s390/pci/pci_event.c

@@ -273,6 +273,8 @@ static void __zpci_event_error(struct zpci_ccdf_err *ccdf)
 	struct zpci_dev *zdev = get_zdev_by_fid(ccdf->fid);
 	struct pci_dev *pdev = NULL;
 	pci_ers_result_t ers_res;
+	u32 fh = 0;
+	int rc;
 
 	zpci_dbg(3, "err fid:%x, fh:%x, pec:%x\n",
 		 ccdf->fid, ccdf->fh, ccdf->pec);
@@ -281,6 +283,15 @@ static void __zpci_event_error(struct zpci_ccdf_err *ccdf)
 
 	if (zdev) {
 		mutex_lock(&zdev->state_lock);
+		rc = clp_refresh_fh(zdev->fid, &fh);
+		if (rc)
+			goto no_pdev;
+		if (!fh || ccdf->fh != fh) {
+			/* Ignore events with stale handles */
+			zpci_dbg(3, "err fid:%x, fh:%x (stale %x)\n",
+				 ccdf->fid, fh, ccdf->fh);
+			goto no_pdev;
+		}
 		zpci_update_fh(zdev, ccdf->fh);
 		if (zdev->zbus->bus)
 			pdev = pci_get_slot(zdev->zbus->bus, zdev->devfn);