fix: addr_validate tests trigger stack/heap buffer overflow under ASAN

[korniltsev-grafanista]

Summary

The validate_stack and validate_heap tests in src/addr_validate.rs both pass pointers to variables smaller than CHECK_LENGTH (16 bytes = 2 × pointer size on 64-bit) to validate().

validate() always reads exactly CHECK_LENGTH = 2 * size_of::<*const c_void>() bytes from the given address via write() to a pipe (the mechanism used to check readability). Both tests therefore read past the end of their variables into the ASAN redzone:

• validate_stack: passes &i where i: i32 (4 bytes) — 12-byte stack-buffer-overflow
• validate_heap: passes &elem for each i32 in a Vec — 12-byte heap-buffer-overflow on the last element

Reproduction

RUSTFLAGS="-Zsanitizer=address" cargo +nightly test --target aarch64-apple-darwin --lib

ASAN reports:

ERROR: AddressSanitizer: stack-buffer-overflow on address ... 
  [32, 36) 'i' (line 115) <== Memory access at offset 36 overflows this variable

Fix

Use variables at least 16 bytes in size:

// validate_stack
let i: [u8; 16] = [0; 16];
assert!(validate(i.as_ptr() as *const libc::c_void));

// validate_heap
let vec: Vec<u128> = vec![0; 1000];

CHECK_LENGTH is 16 bytes because validate() is used to preflight reads of FramePointerLayout (two pointer-sized fields: frame_pointer + ret) before the frame pointer unwinder dereferences them.