[20.0.0]: Backport fixes from main to the release branch #8331
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alexcrichton
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Apr 11, 2024
alexcrichton
commented
- cranelift: Include clobbers and outgoing args in stack limit #8301 - not security related but still a good bug fix to get in earlier
- fix: bindgen trappable_errors using unversion/versioned packages #8305 - this is being backported to 18/19 so also have it present on 20
- Cranelift: Do not dedupe/GVN bitcasts from reference values #8317 - required for safety on the 20 branch
- Handle out-of-bounds component sections #8323 - being backported to 19 so also have in 20
…ealliance#8301) When we compute the amount of space that we need in a stack frame for the stack limit check, we were only counting spill-slots and explicit stack-slots. However, we need to account for all uses of the stack which occur before the next stack limit check. That includes clobbers and any stack arguments we want to pass to callees. The maximum amount that we could have missed by is essentially bounded by the number of arguments which could be passed to a function. In Wasmtime, that is limited by `MAX_WASM_FUNCTION_PARAMS` in `wasmparser::limits`, which is set to 1,000, and the largest arguments are 16-byte vectors, so this could undercount by about 16kB. This is not a security issue according to Wasmtime's security policy (https://docs.wasmtime.dev/security-what-is-considered-a-security-vulnerability.html) because it's the embedder's responsibility to ensure that the stack where Wasmtime is running has enough extra space on top of the configured `max_wasm_stack` size, and getting within 16kB of the host stack size is too small to be safe even with this fixed. However, this was definitely not the intended behavior when stack limit checks or stack probes are enabled, and anyone with non-default configurations or non-Wasmtime uses of Cranelift should evaluate whether this bug impacts your use case. (For reference: When Wasmtime is used in async mode or on Linux, the default stack size is 1.5MB larger than the default WebAssembly stack limit, so such configurations are typically safe regardless. On the other hand, on macOS the default non-async stack size for threads other than the main thread is the same size as the default for `max_wasm_stack`, so that is too small with or without this bug fix.)
…ecodealliance#8305) Signed-off-by: Brian H <brian.hardock@fermyon.com>
…alliance#8317) * Cranelift: Do not dedupe/GVN bitcasts from reference values Deduping bitcasts to integers from references can make the references no long longer live across safepoints, and instead only the bitcasted integer results would be. Because the reference is no longer live after the safepoint, the safepoint's stack map would not have an entry for the reference, which could result in the collector reclaiming an object too early, which is basically a use-after-free bug. Luckily, we sandbox the GC heap now, so such UAF bugs aren't memory unsafe, but they could potentially result in denial of service attacks. Either way, we don't want those bugs! On the other hand, it is technically fine to dedupe bitcasts *to* reference types. Doing so extends, rather than shortens, the live range of the GC reference. This potentially adds it to more stack maps than it otherwise would have been in, which means it might unnecessarily survive a GC it otherwise wouldn't have. But that is fine. Shrinking live ranges of GC references, and removing them from stack maps they otherwise should have been in, is the problematic transformation. * Add additional logging and debug asserts for GC stuff
* Handle out-of-bounds component sections Fixes bytecodealliance#8322 * Add a test that trancated component binaries don't cause panics
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jameysharp
approved these changes
Apr 11, 2024
alexcrichton
merged commit deb0577
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bytecodealliance:release-20.0.0
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