[ptr] Fix soundness hole in "at least" invariants #909
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Previously, we spuriously implemented `at_least::Initialized` for the `Valid` invariant, which is unsound. This was introduced because, prior to the introduction of the `Initialized` invariant, all invariants were monotonic - when defined in the proper order, every invariant was at least as strict as all preceding invariants. Thus, the `define_system!` macro we use to define a system of invariants automatically emitted the appropriate impls based on this monotonicity assumption. `Initialized` broke this assumption, but we didn't update the macro to match. This commit changes the `define_system!` macro to require the caller to explicitly define the "at least" relation. It also adds a test to prevent regressions. As a consequence of making the "at least" relation explicit, we remove the `at_least::Initialized` trait, since this trait would have no non-trivial implementations.
jswrenn
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Feb 18, 2024
dorryspears
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Feb 20, 2024
Previously, we spuriously implemented `at_least::Initialized` for the `Valid` invariant, which is unsound. This was introduced because, prior to the introduction of the `Initialized` invariant, all invariants were monotonic - when defined in the proper order, every invariant was at least as strict as all preceding invariants. Thus, the `define_system!` macro we use to define a system of invariants automatically emitted the appropriate impls based on this monotonicity assumption. `Initialized` broke this assumption, but we didn't update the macro to match. This commit changes the `define_system!` macro to require the caller to explicitly define the "at least" relation. It also adds a test to prevent regressions. As a consequence of making the "at least" relation explicit, we remove the `at_least::Initialized` trait, since this trait would have no non-trivial implementations.
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Previously, we spuriously implemented
at_least::Initializedfor theValidinvariant, which is unsound. This was introduced because, prior to the introduction of theInitializedinvariant, all invariants were monotonic - when defined in the proper order, every invariant was at least as strict as all preceding invariants. Thus, thedefine_system!macro we use to define a system of invariants automatically emitted the appropriate impls based on this monotonicity assumption.Initializedbroke this assumption, but we didn't update the macro to match.This commit changes the
define_system!macro to require the caller to explicitly define the "at least" relation. It also adds a test to prevent regressions.As a consequence of making the "at least" relation explicit, we remove the
at_least::Initializedtrait, since this trait would have no non-trivial implementations.