On Thu, Jul 28, 2016 at 05:42:21PM -0700, William Tu wrote: > The total size of value copy_to_user() writes to userspace should > be the (current number of cpu) * (value size), instead of > num_possible_cpus() * (value size). Found by samples/bpf/test_maps.c, > which always copies 512 byte to userspace, crashing the userspace > program stack.
hmm. I'm missing something. The sample code assumes no cpu hutplug, so sysconf(_SC_NPROCESSORS_CONF) == num_possible_cpu == num_online_cpu, unless there is crazy INIT_ALL_POSSIBLE config option is used.
