Buffer problem

Hi! I have this here:

char* buffer = 0;

// search file in array

for (int i = 0; i < m_files.size(); ++i)
{
	if (!strcmp(m_files[i].Name, Filename))
	{
		// file found in archiv

		// resize buffer

		unsigned int size = m_files[i].Size;
		buffer = (char*) malloc (size);
		// go to dataoffset

		fseek (m_pFile, m_files[i].DataOffset, SEEK_SET);
		// read out of file

		fread (buffer, 1, size, m_pFile);

		// only for debuging

		int a = strlen(buffer);
		if (a) a = 0;
	}
}		

If i run this peace of code with size = 22 then in the end a = 40, but it should also be 22. The buffer contains the correct data, but the last 18 byte there is nonsene. Could somebody help me? Thanks, Christian