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author | Silas Boyd-Wickizer <sbw@mit.edu> | 2012-08-03 19:34:50 (GMT) |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2012-09-23 14:43:56 (GMT) |
commit | 429227bbe55647aa42f8f63cac61e4544e248629 (patch) | |
tree | 345535746085ed30bfea14e38e23c61a540ddbbd /kernel/rcutree_trace.c | |
parent | a2db672aa305a045404615e5222ba681bab6cf58 (diff) | |
download | linux-429227bbe55647aa42f8f63cac61e4544e248629.tar.xz |
Use get_online_cpus to avoid races involving CPU hotplug
If arch/x86/kernel/cpuid.c is a module, a CPU might offline or online
between the for_each_online_cpu() loop and the call to
register_hotcpu_notifier in cpuid_init or the call to
unregister_hotcpu_notifier in cpuid_exit. The potential races can
lead to leaks/duplicates, attempts to destroy non-existant devices, or
random pointer dereferences.
For example, in cpuid_exit if:
for_each_online_cpu(cpu)
cpuid_device_destroy(cpu);
class_destroy(cpuid_class);
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
<----- CPU onlines
unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
the hotcpu notifier will attempt to create a device for the
cpuid_class, which the module already destroyed.
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 'kernel/rcutree_trace.c')
0 files changed, 0 insertions, 0 deletions