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

tip-bot for Masayoshi Mizuma
2018-02-13T12:13:08Z

Commit-ID: 295cc7eb314eb3321fb6d67ca6f7305f5c50d10f
Gitweb: https://git.kernel.org/tip/295cc7eb314eb3321fb6d67ca6f7305f5c50d10f
Author: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
AuthorDate: Thu, 8 Feb 2018 09:19:08 -0500
Committer: Ingo Molnar <mingo@kernel.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@jp.fujitsu.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: yasu.isimatu@gmail.com
Cc: <stable@vger.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@kernel.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();