Fix buffer overflow in block scanner serialize()#1
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open_blocks can grow past the fixed TREE_SITTER_SERIALIZATION_BUFFER_SIZE buffer for deeply nested markdown; memcpy'ing them overflowed the buffer and corrupted the parser's adjacent state. Bail out (serialize no state, so the scanner deserializes fresh) when the state won't fit. Upstream report: tree-sitter-grammars#243
The deep-nesting test aborts on the unguarded scanner (debug tree-sitter asserts in ts_parser__external_scanner_serialize; release builds corrupt parser state instead) and must complete safely with the guard. The moderate-nesting test pins that inputs fitting the buffer still parse cleanly.
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Veykril
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…tries#60312) Zed bundles the markdown grammar's block scanner natively, and its `serialize()` `memcpy`s the open-block stack into tree-sitter's fixed 1024-byte serialization buffer with no bounds check. Markdown with roughly 255+ nested blocks overflows that buffer, and because it sits at the front of `struct TSParser`, the overflow clobbers the adjacent parse-stack pointer and heap. Debug builds of the tree-sitter runtime catch this with an assertion, but release builds like Zed's have no check and silently corrupt parser memory — which is why this surfaced as wild crashes deep in tree-sitter's parse stack rather than clean failures. Still open upstream as tree-sitter-grammars/tree-sitter-markdown#243. This PR points `tree-sitter-md` at a `zed-industries` fork whose `serialize()` refuses to write state that doesn't fit (bounded by the same running counter the header writes advance, so the check can't drift). The scanner then deserializes to a fresh state, and the pathologically nested region surfaces as ordinary tree-sitter `ERROR` nodes — visible, safe degradation for an adversarial input class, deliberately chosen over the two alternatives: truncating the block stack would deserialize into a plausible-but-wrong state and produce silently incorrect trees, and the scanner ABI offers no error channel at all (`serialize()` returns a length into a fixed buffer; there is no way to fail a parse). A nesting-depth cap at block-open time would give fully deterministic semantics, but that's a behavior change across 13 scanner call sites that belongs upstream, not in a hotfix fork. The pinned branch is upstream's `9a23c1a9` (the revision Zed already pinned) plus exactly two commits, for easy review: the guard (zed-industries/tree-sitter-markdown@179422e) and regression tests (zed-industries/tree-sitter-markdown@b596e73). The deep-nesting test aborts on the unguarded scanner and passes with the guard; a moderate-nesting test pins that inputs fitting the buffer still parse cleanly. The same change is also up as zed-industries/tree-sitter-markdown#1 into the fork's default branch (`split_parser`), so future pin bumps don't lose it; if upstream fixes zed-industries#243, we can drop the fork entirely on the next bump. Closes FR-115 Release Notes: - Fixed a potential crash when editing Markdown with deeply nested blocks
TakuroBreath
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…tries#60312) Zed bundles the markdown grammar's block scanner natively, and its `serialize()` `memcpy`s the open-block stack into tree-sitter's fixed 1024-byte serialization buffer with no bounds check. Markdown with roughly 255+ nested blocks overflows that buffer, and because it sits at the front of `struct TSParser`, the overflow clobbers the adjacent parse-stack pointer and heap. Debug builds of the tree-sitter runtime catch this with an assertion, but release builds like Zed's have no check and silently corrupt parser memory — which is why this surfaced as wild crashes deep in tree-sitter's parse stack rather than clean failures. Still open upstream as tree-sitter-grammars/tree-sitter-markdown#243. This PR points `tree-sitter-md` at a `zed-industries` fork whose `serialize()` refuses to write state that doesn't fit (bounded by the same running counter the header writes advance, so the check can't drift). The scanner then deserializes to a fresh state, and the pathologically nested region surfaces as ordinary tree-sitter `ERROR` nodes — visible, safe degradation for an adversarial input class, deliberately chosen over the two alternatives: truncating the block stack would deserialize into a plausible-but-wrong state and produce silently incorrect trees, and the scanner ABI offers no error channel at all (`serialize()` returns a length into a fixed buffer; there is no way to fail a parse). A nesting-depth cap at block-open time would give fully deterministic semantics, but that's a behavior change across 13 scanner call sites that belongs upstream, not in a hotfix fork. The pinned branch is upstream's `9a23c1a9` (the revision Zed already pinned) plus exactly two commits, for easy review: the guard (zed-industries/tree-sitter-markdown@179422e) and regression tests (zed-industries/tree-sitter-markdown@b596e73). The deep-nesting test aborts on the unguarded scanner and passes with the guard; a moderate-nesting test pins that inputs fitting the buffer still parse cleanly. The same change is also up as zed-industries/tree-sitter-markdown#1 into the fork's default branch (`split_parser`), so future pin bumps don't lose it; if upstream fixes zed-industries#243, we can drop the fork entirely on the next bump. Closes FR-115 Release Notes: - Fixed a potential crash when editing Markdown with deeply nested blocks
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The block scanner's
serialize()copiesopen_blocksinto tree-sitter's fixedTREE_SITTER_SERIALIZATION_BUFFER_SIZE(1024-byte) buffer with no bounds check. Deeply nested markdown (roughly 255+ open blocks) overflows the buffer; since it lives at the front ofstruct TSParser, the overflow clobbers the adjacent parse-stack pointer and heap, corrupting the parser and crashing later inside tree-sitter's stack management. This bails out of serialization when the state won't fit (serializing zero bytes, so the scanner deserializes to a fresh state) rather than writing out of bounds — degraded incremental-parse fidelity in that pathological case, instead of memory corruption.Reported upstream as tree-sitter-grammars#243. Zed currently pins this same fix rebased onto its pinned revision
9a23c1a(commit9506f128, via zed-industries/zed#60312); this PR brings it ontosplit_parserso the fork's default branch carries it and future pin bumps don't lose it.