Patch "x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU" has been added to the 4.15-stable tree
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This is a note to let you know that I've just added the patch titled
x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU
to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-smpboot-fix-uncore_pci_remove-indexing-bug-when-hot-removing-a-physical-cpu.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
295cc7eb314eb3321fb6d67ca6f7305f5c50d10fMon Sep 17 00:00:00 2001
From: Masayoshi Mizuma <[email protected]>
Date: Thu, 8 Feb 2018 09:19:08 -0500
Subject: x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU
From: Masayoshi Mizuma <[email protected]>
commit 295cc7eb314eb3321fb6d67ca6f7305f5c50d10f upstream.
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.
--- arch/x86/kernel/smpboot.c | 1 - 1 file changed, 1 deletion(-)
arch/x86/kernel/smpboot.c +0 -1
@@ -1431,7 +1431,6 @@ 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 ();
Patches currently in stable-queue which might be from [email protected] are
queue-4.15/x86-smpboot-fix-uncore_pci_remove-indexing-bug-when-hot-removing-a-physical-cpu.patch