- it cannot branch backwards (this is also true of eBPF)
  - it can only do ternary operator branches
  - it cannot define functions
  - functions it can call are limited to some builtin ones
  - it can only scribble on the one pre-allocated probe buffer
  - it can only access the probe's defined parameters

This working model significantly increases the attack surface of the kernel, since it allows executing arbitrary code at a high privilege level. Because of this risk, programs have to be verified before they can be loaded. This ensures that all eBPF security assumptions are met. The verifier, which consists of complex code, is responsible for this task.

Given how difficult the task of validating that a program is safe to execute is, there have been many vulnerabilities found within the eBPF verifier. When one of these vulnerabilities is exploited, the result is usually a local privilege escalation exploit (or container escape in containerized environments). While the verifier’s code has been audited extensively, this task also becomes harder as new features are added to eBPF and the complexity of the verifier grows

DTrace was developed over 20 years ago; there have not been "many vulnerabilities" found in the verifier -- and we have not grown the complexity of the verifier over time. You can dismiss these as implementation details, but these details reflect different views of the problem and its contraints.