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revive/crates/integration/contracts/FnNativeFmpBug.yul
T
xermicusandClaude Opus 4.8 61b7ab8521 Fix/ny fn native fmp oog (#567)
Bug found by @jubnzv:

`--newyork`: a full-width value stored to the free-memory-pointer slot
(e.g. a function parameter `>= 2^64`) was narrowed to 64 bits, inserting
a checked truncation that consumed all gas.

---------

Signed-off-by: xermicus <bigcyrill@hotmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-08 17:41:05 +02:00

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/// Soundness PoC (newyork type inference): a value stored to the free-memory-pointer
/// slot `0x40` must not be narrowed to a 64-bit pointer width when it is also
/// observable at full width elsewhere.
///
/// `f0`'s parameter `p0` is stored to the FMP slot (`mstore(64, p0)`) — which
/// inference treated as a bounded pointer and narrowed to i64 — but `p0` is also
/// stored full-width at offset 8 and read back by `mload(24)`. The i64 narrowing
/// of the parameter inserts a call-boundary guard that traps (consumes all gas)
/// when a caller passes an argument `>= 2^64`. The first call passes `b`
/// (`calldataload(32)`, a full 256-bit word), so newyork ran out of gas where EVM
/// (and the stock pipeline) execute successfully. The fix records the FMP-stored
/// value as an ordinary full-width memory value.
object "FnNativeFmpBug" {
code { datacopy(0, dataoffset("FnNativeFmpBug_deployed"), datasize("FnNativeFmpBug_deployed")) return(0, datasize("FnNativeFmpBug_deployed")) }
object "FnNativeFmpBug_deployed" {
code {
let a := calldataload(0) let b := calldataload(32) let d := calldataload(96) let r := 0
function f0(p0, p1) -> ret {
mstore(8, p0)
mstore(64, p0)
mstore8(8, p1)
ret := mload(24)
}
r := add(mul(r, 0x100000001b3), f0(b, a))
r := add(mul(r, 0x100000001b3), f0(2719014241053524200, d))
r := add(mul(r, 0x100000001b3), f0(391540675041506305, b))
mstore(0, r)
return(0, 32)
}
}
}