About
Stack clash is an exploit which utilized large frame allocations to "jump the guard page" creating a scenario where the heap and stack collided under attacker control. This can be used to gain full control of a vulnerable application. Stack probing techniques can be used to mitigate the vast majority of vulnerabilities in this space, but implementing them requires significant work for each and every target to be supported.
Stack class mitigations are a soft requirement for distributions such as Fedora and a hard requirement for Red Hat Enterprise Linux.
Stakeholders/Partners
RISE:
Ventana: Raphael Zinsly – lead developer
Ventana: Jeff Law – design/implementation review
External:
Dependencies
- There is a minor dependency on wording in PSABI for a extreme corner case. Essentially PSABI will need to spell out certain requirements for callers that the callee can depend on to implement efficient stack clash mitigation. This is a technical ABI change, but it is expected all binaries in the wild would satisfy the new ABI requirements as-is without a rebuild.
Status
Updates
- The stack-clash implementation bootstraps when on by default
- It appears that the implementation works correctly for the smoke test (realpath in glibc)
- GCC's testsuite for stack clash is passing at this point
- Building scanning tools to help identify vulnerable code and verify that the implementation closes the vulnerability
- Upstreaming plan: late spring, shortly after gcc-15 opens for develoment
- Implementation of naive protection making good progress. Handles scalar and vector (following the aarch64 implementation for vector in particular)
- Probing of outgoing argument area not started
- Kito is aware of need to make minor changes to PSABI to document expectations from compilers
- Project reported as priority for 1H2024.