node:http: copy the HTTPParser input when a callback can unmap it

[robobun]

Problem

• HTTPParser.prototype.execute(view) (process.binding("http_parser"), the parser behind node:_http_common) crashes the main thread when a parser callback releases the input: SEGV READ in llhttp__internal__run (llhttp.c:1362), under Bun::HTTPParser::execute.
• jsHTTPParser_execute gives llhttp the view's raw pointer and length for the whole run (JSHTTPParserPrototype.cpp:140). kOnHeadersComplete and kOnBody run user JS in the middle of that run.
• The pin() above it only makes ArrayBuffer.prototype.transfer() copy. It stops neither resize() on a resizable ArrayBuffer nor the detach that WebAssembly.Memory.prototype.grow() performs.

Fix

• Copy the input into a WTF::Vector<uint8_t> that lives for the whole call when the backing buffer is a resizable non-shared ArrayBuffer or a WebAssembly.Memory. Every other buffer keeps the pin and is read in place, so a socket read still does not copy.
• One copy covers every borrow of those bytes in a run: llhttp's own cursor, the header and URL spans that save() copies at the end, and getCurrentBuffer().
• Those two kinds are the ones JSC can release while the buffer is pinned. A growable SharedArrayBuffer grows in place and keeps its pointer, so it is read in place.
• Verified: test/js/node/http/node-http-parser.test.ts, two new cases (resizable and wasm), each fails on stock bun. Also ran all of test/js/node/http and the node test-http-parser tests. Self-reviewed: 6 concerns, all about a wider scope, answered in the notes.

Background

• llhttp is a C parser. It scans the caller's bytes and calls back per message part. A callback runs user JS, then llhttp keeps reading from the same pointer.
• A pin on a JSC ArrayBuffer blocks a detach only. isDetachable() is read by transferTo, not by resize() and not by the wasm grow path.
• A resizable ArrayBuffer decommits its trimmed pages, so a read after resize(0) faults. A bounds-checked WebAssembly.Memory can move its bytes when it grows.

Notes

Reproduction (both cases are in the new test):

const { HTTPParser } = process.binding("http_parser");
const size = 1024 * 1024;
const buffer = new ArrayBuffer(size, { maxByteLength: size });
const bytes = new Uint8Array(buffer);
// a chunked POST that fills `bytes`
const parser = new HTTPParser();
parser.initialize(HTTPParser.REQUEST, {});
parser[HTTPParser.kOnHeadersComplete] = () => 0;
parser[HTTPParser.kOnBody] = () => buffer.resize(0); // llhttp keeps scanning the trimmed pages
parser.execute(bytes);

Verification:

• bun bd (debug, ASAN), resizable: AddressSanitizer: SEGV on unknown address, READ, #0 llhttp__internal__run llhttp.c:1362.
• Local release build (1.4.3-canary), resizable: panic(main thread): Segmentation fault, 4/4 runs.
• Local release build, wasm: no crash, but the parse walks the released block and returns HPE_STRICT: Expected LF after chunk data after the first body callback, 2/2 runs.
• With src/ reverted to the base commit, bun bd test test/js/node/http/node-http-parser.test.ts fails the resizable case. With the fix, all 22 tests in the file pass.
• bun bd test test/js/node/http: 356 pass. The one failure (node-http-syscall-fault.test.ts, "queued drain", a subprocess test with a 5 s timeout) fails the same way with src/ reverted, so it is not from this change.

Why copy instead of re-reading the live extent after each callback: llhttp resumes from its own saved pointer as soon as a callback returns, and the parser holds more borrows of the same bytes than that cursor. m_url, m_statusMessage and the header StringPtr entries point into the input until save() copies them at the end of execute(), and getCurrentBuffer() memcpys out of m_currentBufferData while a callback runs. A copy with the same lifetime as the call fixes all of them at once. A getCurrentBuffer() call in a callback that follows resize(0) segfaults on stock bun too, and the new test asserts its length.

Same shape as existing code for this hazard: PinnedArrayBuffer::copy_if_resizable in src/jsc/array_buffer.rs ("a pin stops a detach but not a shrink, which unmaps pages") and the changeset copy in src/jsc/bindings/sqlite/NodeSqlite.cpp, where SQLite streams from a buffer while its callbacks re-enter JS.

The copy is conditional on purpose. node:_http_common calls execute() with a plain socket Buffer on every read, so an unconditional copy would memcpy every HTTP read.

Scope. This PR fixes the llhttp borrow only. #42192 is the umbrella pass for this class and lists this file as not covered by it. Two same-class sites stay open and are not in this diff: Bun.markdown.{html,ansi,render,react} (src/runtime/api/MarkdownObject.rs:68, which uses the pin-only PinnedArrayBuffer::pin while its render callbacks run user JS per element), and Transpiler.scan / transformSync. When the second of #42192 and this PR lands, the isResizableNonShared() || isWasmMemory() test is worth hoisting into one named helper next to pinStorage() in bindings.cpp, so the three current spellings of it (here, copy_if_resizable in src/jsc/array_buffer.rs, and #42192's) become one.

---

[human-review] gate passed · iteration 0 · 2 files touched

fails on main (without fix)

ASAN without fix: 2 FAILED
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/js/node/http/node-http-parser.test.ts
bun test v1.4.3 (5f554969b)

test/js/node/http/node-http-parser.test.ts:
(pass) method lists > contain M-SEARCH, not a malformed token [14.13ms]
(pass) method lists > contain no whitespace in any method token [16.95ms]
(pass) HTTPParser.prototype.close > does not double free [1.89ms]
(pass) HTTPParser.prototype.close > does not segfault calling other methods after close [5.15ms]
(pass) HTTPParser before initialize() > execute() and finish() throw instead of running over uninitialised state [262.98ms]
(pass) HTTPParser.prototype.finish > reports bytesParsed of 0 when finish() fails after a paused parse [4.64ms]
(pass) HTTPParser.prototype.finish > returns error for invalid state [9.33ms]
(pass) HTTPParser.prototype.finish > basic [1.99ms]
(pass) HTTPParser.prototype.execute > keeps the input buffer attached when a callback transfers it mid-parse [12.04ms]
269 | 
270 |       const chunks = Math.floor((inputSizes[mode] - head.length - tail.length) / chunkSize);
271 | 
272 |       // `executed` cov
... (truncated)

release without fix: 2 FAILED
bun test v1.4.3-canary.1 (5f554969b)

test/js/node/http/node-http-parser.test.ts:
(pass) method lists > contain M-SEARCH, not a malformed token [0.02ms]
(pass) method lists > contain no whitespace in any method token [0.10ms]
(pass) HTTPParser.prototype.close > does not double free [0.02ms]
(pass) HTTPParser.prototype.close > does not segfault calling other methods after close [0.04ms]
(pass) HTTPParser before initialize() > execute() and finish() throw instead of running over uninitialised state [4.42ms]
(pass) HTTPParser.prototype.finish > reports bytesParsed of 0 when finish() fails after a paused parse [0.08ms]
(pass) HTTPParser.prototype.finish > returns error for invalid state [0.14ms]
(pass) HTTPParser.prototype.finish > basic [0.02ms]
(pass) HTTPParser.prototype.execute > keeps the input buffer attached when a callback transfers it mid-parse [0.18ms]
269 | 
270 |       const chunks = Math.floor((inputSizes[mode] - head.length - tail.length) / chunkSize);
271 | 
272 |       // `executed` covers the whole request, so llhttp read every chunk that follows the callback
273 |       // which unmapped the input, and each one held the bytes the request was built with
... (truncated)

passes on PR (with fix)

ASAN with fix: all passed
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" test/js/node/http/node-http-parser.test.ts
bun test v1.4.3 (5f554969b)

test/js/node/http/node-http-parser.test.ts:
(pass) method lists > contain M-SEARCH, not a malformed token [2.22ms]
(pass) method lists > contain no whitespace in any method token [28.64ms]
(pass) HTTPParser.prototype.close > does not double free [2.99ms]
(pass) HTTPParser.prototype.close > does not segfault calling other methods after close [4.75ms]
(pass) HTTPParser before initialize() > execute() and finish() throw instead of running over uninitialised state [273.83ms]
(pass) HTTPParser.prototype.finish > reports bytesParsed of 0 when finish() fails after a paused parse [4.53ms]
(pass) HTTPParser.prototype.finish > returns error for invalid state [9.05ms]
(pass) HTTPParser.prototype.finish > basic [1.93ms]
(pass) HTTPParser.prototype.execute > keeps the input buffer attached when a callback transfers it mid-parse [12.08ms]
(pass) HTTPParser.prototype.execute > finishes the parse when a callback unmaps the input (resizable) [454.38ms]
(pass) HTTPParser.prototype.ex
... (truncated)

release with fix: all passed
$ bun scripts/build.ts --profile=release
[configured] bun-profile → bun (stripped)
  target       linux-x64-gnu
  build type   Release
  build dir    ./build/release
  revision     f244f258ec
  features     baseline

23 deps, 131 codegen, 1172 objects in 657ms

ninja: Entering directory `/workspace/bun/build/release'
[1/1244] install /workspace/bun
bun install v1.4.3-canary.1 (5f554969b)

Checked 22 installs across 61 packages (no changes) [9.00ms]
[2/1244] install /workspace/bun/packages/bun-error
bun install v1.4.3-canary.1 (5f554969b)

Checked 1 install across 2 packages (no changes) [5.00ms]
[3/1244] gen ErrorCode+*.h
[4/1244] fetch zlib
[zlib] up to date
[5/1244] gen bindgenv2
[6/1244] gen .bind.ts → GeneratedBindings.cpp
[7/1244] install /workspace/bun/src/node-fallbacks
bun install v1.4.3-canary.1 (5f554969b)

Checked 111 installs across 104 packages (no changes) [3.00ms]
[8/1244] gen node-fallbacks/react-refresh.js
Bundled 1 module in 12ms

  react-refresh.js  4.81 KB  (entry point)

[9/1244] gen bake.{client,server,error}.js
-> bake.client.js, bake.server.js, bake.error.js
[10/1244] fetch libjpeg-turbo
[libjpeg-turbo] up to date
[11/1217] fetch tinycc
[
... (truncated)

diff hotspot

.../bindings/node/http/JSHTTPParserPrototype.cpp   |  21 ++++-
 test/js/node/http/node-http-parser.test.ts         | 103 +++++++++++++++++++++
 2 files changed, 121 insertions(+), 3 deletions(-)

gate history · 1 passed · 0 rejected · iteration 0

evidence per changed file

file                                                  reads  edits  tests
src/jsc/bindings/node/http/JSHTTPParserPrototype.cpp      2      5     22
test/js/node/http/node-http-parser.test.ts                2      8     22

[robobun]

^{Updated 4:24 AM PT - Sep 10th, 2026}

✅ @robobun, your commit f244f258eca9e6e9397a56cc4d7769b80faddace passed in Build #113812! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 42194

That installs a local version of the PR into your bun-42194 executable, so you can run:

bun-42194 --bun

[robobun]

Status

• Closed. The same change landed on main through node:http: the server follows Node (request body, framing, response finish, lifecycle) #43557 (5d5f03f), with both test cases.
• Found by fuzzing process.binding("http_parser"). Reproduced on main (4ff9193) under ASAN: SEGV READ in llhttp__internal__run (llhttp.c:1362), and on a release build as panic(main thread): Segmentation fault.
• Fail-before proof: with src/ at the base commit, bun bd test test/js/node/http/node-http-parser.test.ts fails the resizable case. With the fix, all 22 tests in that file pass.

[coderabbitai]

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Walkthrough

Changes

The HTTP parser now protects input from invalidation when callbacks resize ArrayBuffer or grow WebAssembly memory. Regression tests cover both cases and verify parsing results.

HTTP parser input lifetime

Layer / File(s)	Summary
Input storage selection src/jsc/bindings/node/http/JSHTTPParserPrototype.cpp	jsHTTPParser_execute copies affected input into owned storage, retains pinning for other buffers, reports allocation failure, and passes the selected span to llhttp.
Memory mutation regression tests test/js/node/http/node-http-parser.test.ts	Child-process tests resize an ArrayBuffer or grow WebAssembly memory during callbacks and verify parsing, byte counts, body data, completion, and current-buffer handling.

Merge Risk: ⚪ Minimal · up to af439

The parser now protects resizable input from callback-driven invalidation while preserving existing behavior for other buffers. Regression coverage passes, so no material merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the main change: copying HTTPParser input when callbacks can invalidate the backing memory.
Description check	✅ Passed	The description explains the problem, fix, scope, regression tests, and verification results. It does not use the exact template headings, but it provides the required information in equivalent sectio…

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@test/js/node/http/node-http-parser.test.ts`:
- Around line 208-211: Update the WebAssembly memory setup around the
signaling-memory pool and memory.grow(1) so the test directly verifies that the
original allocation was relocated or unmapped, rather than relying on the old
buffer’s detached state. Replace the hard-coded hold count with a configuration
tied to the bounds-checking behavior or add an explicit relocation/unmapping
assertion, while preserving the regression coverage for the parser’s
stale-pointer failure.

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[claude]

Code review found no issues

No high-confidence issues detected in this change.

[Jarred-Sumner]

Superseded by #43557, which is merged (5d5f03f). It fixes this once for the whole node:http server and carries the tests over.

[robobun]

Confirmed on main (5d5f03f).

• src/jsc/bindings/node/http/JSHTTPParserPrototype.cpp is identical to this branch.
• Both test cases are in test/js/node/http/node-http-parser.test.ts, unchanged.
• CI for node:http: the server follows Node (request body, framing, response finish, lifecycle) #43557 ran them. Build 120883 passed.

Nothing is left to do for this report.