[GitHub] [incubator-teaclave-sgx-sdk] duanbing edited a comment on issue #251: libc::free core dump due to invalid address

[GitBox <gi...@apache.org>]

duanbing edited a comment on issue #251:
URL: https://github.com/apache/incubator-teaclave-sgx-sdk/issues/251#issuecomment-647835021


   > > ```
   > > void ocall_free([user_check]void* p);
   > > -----
   > > #[no_mangle]
   > > pub extern "C" fn ocall_free(p: *mut libc::c_void) {
   > >    println!("addr: {:?}", p);
   > >    unsafe { libc::free(p) }
   > > }   
   > > ```
   > 
   > before you call `ocall-free`, what is the pointer's value? is it pointing to an unsafe buffer? can i pass the sgx_is_outside_enclave check?
   
   ```
   ....
           let mut output = 0 as *mut libc::c_void;
          
           let mut out_len: usize = 0;
           let resp = unsafe {
               ocall_call(&mut rt,
                                          req.as_ptr() as *const u8,
                                          req.len(),
                                          &mut output,
                                          &mut out_len)
           };
          
           // TODO resp和rt都要判断
           match resp {
               sgx_status_t::SGX_SUCCESS => {
                   ....
                  
                   println!("before free: {:?}", output);
                   let mut rt : sgx_status_t = sgx_status_t::SGX_ERROR_UNEXPECTED;
                   unsafe{ocall_free(&mut rt, output)};
                   ..
   
                   Ok(xxxx)
               },
   ...
   ```


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