What might happen if processes access each other's memory space?

When processes access each other's memory space, there is a significant risk of instability within the operating system, which can lead to potential crashes. This is due to the fact that one process could accidentally or maliciously modify the data of another process, causing unpredictable behavior or failures. This type of interference undermines the isolation that normally exists between processes, which is critical for maintaining the integrity of the system.

Moreover, accessing another process's memory can also lead to violations of confidentiality. If process A can read the memory space of process B, it might gain access to sensitive information such as passwords, private data, or secure tokens that are not meant to be shared. This breach of confidentiality can lead to serious security vulnerabilities, where sensitive information is exposed to unauthorized entities.

While one might assume that allowing memory access could improve performance (for instance, by sharing data), the risks associated with crashes and confidentiality breaches outweigh any potential benefits. Therefore, allowing processes to freely access one another's memory is contrary to sound operating system design principles aimed at ensuring security and stability.