platform/x86/intel/pmt: fix a crashlog NULL pointer access

JIRA: https://issues.redhat.com/browse/RHEL-120895

commit 54d5cd4
Author: Michael J. Ruhl <[email protected]>
Date:   Sun Jul 13 13:29:31 2025 -0400

    platform/x86/intel/pmt: fix a crashlog NULL pointer access

    Usage of the intel_pmt_read() for binary sysfs, requires a pcidev. The
    current use of the endpoint value is only valid for telemetry endpoint
    usage.

    Without the ep, the crashlog usage causes the following NULL pointer
    exception:

    BUG: kernel NULL pointer dereference, address: 0000000000000000
    Oops: Oops: 0000 [#1] SMP NOPTI
    RIP: 0010:intel_pmt_read+0x3b/0x70 [pmt_class]
    Code:
    Call Trace:
     <TASK>
     ? sysfs_kf_bin_read+0xc0/0xe0
     kernfs_fop_read_iter+0xac/0x1a0
     vfs_read+0x26d/0x350
     ksys_read+0x6b/0xe0
     __x64_sys_read+0x1d/0x30
     x64_sys_call+0x1bc8/0x1d70
     do_syscall_64+0x6d/0x110

    Augment struct intel_pmt_entry with a pointer to the pcidev to avoid
    the NULL pointer exception.

    Fixes: 045a513 ("platform/x86/intel/pmt: Use PMT callbacks")
    Cc: [email protected]
    Reviewed-by: David E. Box <[email protected]>
    Reviewed-by: Tejas Upadhyay <[email protected]>
    Signed-off-by: Michael J. Ruhl <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]
    Reviewed-by: Ilpo Järvinen <[email protected]>
    Signed-off-by: Ilpo Järvinen <[email protected]>

Signed-off-by: David Arcari <[email protected]>

Author: darcari

drivers/platform/x86/intel/pmt/class.c

@@ -99,7 +99,7 @@ intel_pmt_read(struct file *filp, struct kobject *kobj,
 	if (count > entry->size - off)
 		count = entry->size - off;
 
-	count = pmt_telem_read_mmio(entry->ep->pcidev, entry->cb, entry->header.guid, buf,
+	count = pmt_telem_read_mmio(entry->pcidev, entry->cb, entry->header.guid, buf,
 				    entry->base, off, count);
 
 	return count;
@@ -283,6 +283,7 @@ static int intel_pmt_populate_entry(struct intel_pmt_entry *entry,
 		return -EINVAL;
 	}
 
+	entry->pcidev = pci_dev;
 	entry->guid = header->guid;
 	entry->size = header->size;
 	entry->cb = ivdev->priv_data;

drivers/platform/x86/intel/pmt/class.h

@@ -40,6 +40,7 @@ struct intel_pmt_header {
 
 struct intel_pmt_entry {
 	struct telem_endpoint	*ep;
+	struct pci_dev		*pcidev;
 	struct intel_pmt_header	header;
 	struct bin_attribute	pmt_bin_attr;
 	struct kobject		*kobj;