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author | Silas Boyd-Wickizer <sbw@mit.edu> | 2012-08-03 12:34:50 -0700 |
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committer | Viresh Kumar <viresh.kumar@linaro.org> | 2012-10-03 14:19:35 +0530 |
commit | 517ddd9e74294e42166161114226f3315c8d1376 (patch) | |
tree | 7a798f7115448ae32a2b8ed954197cd0d9da4aaf /arch/sparc | |
parent | f7210fc689de3ce5c3384591afeb54ead0f28699 (diff) |
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>
Diffstat (limited to 'arch/sparc')
0 files changed, 0 insertions, 0 deletions