summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/msr.c
diff options
context:
space:
mode:
authorSilas Boyd-Wickizer <sbw@mit.edu>2012-08-03 23:33:27 +0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-09-23 18:43:56 +0400
commita2db672aa305a045404615e5222ba681bab6cf58 (patch)
tree49ac9a38d87e42695f212b730751dfa78cf3a0d4 /arch/x86/kernel/msr.c
parent5d18023294abc22984886bd7185344e0c2be0daf (diff)
downloadlinux-a2db672aa305a045404615e5222ba681bab6cf58.tar.xz
Use get_online_cpus to avoid races involving CPU hotplug
If arch/x86/kernel/msr.c is a module, a CPU might offline or online between the for_each_online_cpu(i) loop and the call to register_hotcpu_notifier in msr_init or the call to unregister_hotcpu_notifier in msr_exit. The potential races can lead to leaks/duplicates, attempts to destroy non-existant devices, or random pointer dereferences. For example, in msr_init if: for_each_online_cpu(i) { err = msr_device_create(i); if (err != 0) goto out_class; } <----- CPU offlines register_hotcpu_notifier(&msr_class_cpu_notifier); and the CPU never onlines before msr_exit, then the module will never call msr_device_destroy for the associated CPU. This fix surrounds for_each_online_cpu and register_hotcpu_notifier or unregister_hotcpu_notifier with get_online_cpus+put_online_cpus. Tested on a VM. Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'arch/x86/kernel/msr.c')
-rw-r--r--arch/x86/kernel/msr.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index eb113693f043..a7c5661f8496 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -257,12 +257,14 @@ static int __init msr_init(void)
goto out_chrdev;
}
msr_class->devnode = msr_devnode;
+ get_online_cpus();
for_each_online_cpu(i) {
err = msr_device_create(i);
if (err != 0)
goto out_class;
}
register_hotcpu_notifier(&msr_class_cpu_notifier);
+ put_online_cpus();
err = 0;
goto out;
@@ -271,6 +273,7 @@ out_class:
i = 0;
for_each_online_cpu(i)
msr_device_destroy(i);
+ put_online_cpus();
class_destroy(msr_class);
out_chrdev:
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
@@ -281,11 +284,13 @@ out:
static void __exit msr_exit(void)
{
int cpu = 0;
+ get_online_cpus();
for_each_online_cpu(cpu)
msr_device_destroy(cpu);
class_destroy(msr_class);
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
unregister_hotcpu_notifier(&msr_class_cpu_notifier);
+ put_online_cpus();
}
module_init(msr_init);