s2n_random.c crashes with invalid zero_if_forked_ptr value on x86_64 Android emulator

[chaoamazon]

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If you discover a potential security issue in s2n we ask that you notify
AWS Security via our vulnerability reporting page. Please do not create a public github issue.

Problem:

s2n_random.c crashes on x86_64 Android emulator during fork. It crashes in two places, all when zero_if_forked is accessed. zero_if_forked_ptr always points to invalid address when this happens.

Trace:
1 (s2n_rand_init+224)
2 (s2n_init+26)
3 (aws_tls_init_static_state+124)
4 (aws_mqtt_library_init+33)
5 (Aws::InitializeCrt()+55)
6 (Aws::InitAPI(Aws::SDKOptions const&)+24)

Solution:

A description of the possible solution in terms of S2N architecture. Highlight and explain any potentially controversial design decisions taken.

• Does this change what S2N sends over the wire? If yes, explain.
• Does this change any public APIs? If yes, explain.
• Which versions of TLS will this impact?

Requirements / Acceptance Criteria:

S2n should not crash.

What must a solution address in order to solve the problem? How do we know the solution is complete?
S2n doesn't crash.

• RFC links: Links to relevant RFC(s)
• Related Issues: Link any relevant issues
• Will the Usage Guide or other documentation need to be updated?
• Testing: How will this change be tested? Call out new integration tests, functional tests, or particularly interesting/important unit tests.
  • Will this change trigger SAW changes? Changes to the state machine, the s2n_handshake_io code that controls state transitions, the DRBG, or the corking/uncorking logic could trigger SAW failures.
  • Should this change be fuzz tested? Will it handle untrusted input? Create a separate issue to track the fuzzing work.

Out of scope:

Is there anything the solution will intentionally NOT address?

[dougch]

Thanks for issue- Can you see if the changes in #3191 will help ?