Data Race in x86/x64 pointer to function CPU dispatching

[Nick-Kooij]

There is a data race in blake2-dispatch.c x86/x64 pointer to function CPU dispatching.

Internal calls are made through function pointers to functions that initially point to corresponding dispatch function that detects the CPU features available and updates the corresponding pointer to function.

For example blake2b_init_ptr initially points to blake2b_init_dispatch. The data race is the blake2b_init_ptr pointer update:

int blake2b_init_dispatch( blake2b_state *S, size_t outlen )
{
  /* data race, non-atomic write to blake2b_init_ptr */
  blake2b_init_ptr = blake2b_init_table[get_cpu_features()]; /*
  return blake2b_init_ptr( S, outlen );
}

All *_dispatch functions are likewise affected:

• blake2b_init_dispatch
• blake2b_init_key_dispatch
• blake2b_init_param_dispatch
• blake2b_update_dispatch
• blake2b_final_dispatch
• blake2b_dispatch
• blake2s_init_dispatch
• blake2s_init_key_dispatch
• blake2s_init_param_dispatch
• blake2s_update_dispatch
• blake2s_final_dispatch
• blake2s_dispatch