linux-kernel - [tip:x86/urgent] x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU

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Date:   Tue, 13 Feb 2018 04:13:08 -0800
From:   tip-bot for Masayoshi Mizuma <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...nel.org,
        hpa@...or.com, stable@...r.kernel.org, peterz@...radead.org,
        m.mizuma@...fujitsu.com, torvalds@...ux-foundation.org
Subject: [tip:x86/urgent] x86/smpboot: Fix uncore_pci_remove() indexing bug
 when hot-removing a physical CPU

Commit-ID:  295cc7eb314eb3321fb6d67ca6f7305f5c50d10f
Gitweb:     https://git.kernel.org/tip/295cc7eb314eb3321fb6d67ca6f7305f5c50d10f
Author:     Masayoshi Mizuma <m.mizuma@...fujitsu.com>
AuthorDate: Thu, 8 Feb 2018 09:19:08 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 13 Feb 2018 12:47:28 +0100

x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU

When a physical CPU is hot-removed, the following warning messages
are shown while the uncore device is removed in uncore_pci_remove():

  WARNING: CPU: 120 PID: 5 at arch/x86/events/intel/uncore.c:988
  uncore_pci_remove+0xf1/0x110
  ...
  CPU: 120 PID: 5 Comm: kworker/u1024:0 Not tainted 4.15.0-rc8 #1
  Workqueue: kacpi_hotplug acpi_hotplug_work_fn
  ...
  Call Trace:
  pci_device_remove+0x36/0xb0
  device_release_driver_internal+0x145/0x210
  pci_stop_bus_device+0x76/0xa0
  pci_stop_root_bus+0x44/0x60
  acpi_pci_root_remove+0x1f/0x80
  acpi_bus_trim+0x54/0x90
  acpi_bus_trim+0x2e/0x90
  acpi_device_hotplug+0x2bc/0x4b0
  acpi_hotplug_work_fn+0x1a/0x30
  process_one_work+0x141/0x340
  worker_thread+0x47/0x3e0
  kthread+0xf5/0x130

When uncore_pci_remove() runs, it tries to get the package ID to
clear the value of uncore_extra_pci_dev[].dev[] by using
topology_phys_to_logical_pkg(). The warning messesages are
shown because topology_phys_to_logical_pkg() returns -1.

  arch/x86/events/intel/uncore.c:
  static void uncore_pci_remove(struct pci_dev *pdev)
  {
  ...
          phys_id = uncore_pcibus_to_physid(pdev->bus);
  ...
                  pkg = topology_phys_to_logical_pkg(phys_id); // returns -1
                  for (i = 0; i < UNCORE_EXTRA_PCI_DEV_MAX; i++) {
                          if (uncore_extra_pci_dev[pkg].dev[i] == pdev) {
                                  uncore_extra_pci_dev[pkg].dev[i] = NULL;
                                  break;
                          }
                  }
                  WARN_ON_ONCE(i >= UNCORE_EXTRA_PCI_DEV_MAX); // <=========== HERE!!

topology_phys_to_logical_pkg() tries to find
cpuinfo_x86->phys_proc_id that matches the phys_pkg argument.

  arch/x86/kernel/smpboot.c:
  int topology_phys_to_logical_pkg(unsigned int phys_pkg)
  {
          int cpu;

          for_each_possible_cpu(cpu) {
                  struct cpuinfo_x86 *c = &cpu_data(cpu);

                  if (c->initialized && c->phys_proc_id == phys_pkg)
                          return c->logical_proc_id;
          }
          return -1;
  }

However, the phys_proc_id was already set to 0 by remove_siblinginfo()
when the CPU was offlined.

So, topology_phys_to_logical_pkg() cannot find the correct
logical_proc_id and always returns -1.

As the result, uncore_pci_remove() calls WARN_ON_ONCE() and the warning
messages are shown.

What is worse is that the bogus 'pkg' index results in two bugs:

 - We dereference uncore_extra_pci_dev[] with a negative index
 - We fail to clean up a stale pointer in uncore_extra_pci_dev[][]

To fix these bugs, remove the clearing of ->phys_proc_id from remove_siblinginfo().

This should not cause any problems, because ->phys_proc_id is not
used after it is hot-removed and it is re-set while hot-adding.

Signed-off-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: yasu.isimatu@...il.com
Cc: <stable@...r.kernel.org>
Fixes: 30bb9811856f ("x86/topology: Avoid wasting 128k for package id array")
Link: http://lkml.kernel.org/r/ed738d54-0f01-b38b-b794-c31dc118c207@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/smpboot.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6f27fac..cfc61e1 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1430,7 +1430,6 @@ static void remove_siblinginfo(int cpu)
 	cpumask_clear(cpu_llc_shared_mask(cpu));
 	cpumask_clear(topology_sibling_cpumask(cpu));
 	cpumask_clear(topology_core_cpumask(cpu));
-	c->phys_proc_id = 0;
 	c->cpu_core_id = 0;
 	cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);
 	recompute_smt_state();