TextEncoderStream: throw out of memory instead of aborting when a chunk's output buffer cannot be allocated - #38941
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…nstead of aborting TextEncoderStream's encoder reserved its output buffers infallibly, so a chunk whose encoding did not fit in memory aborted the process. Reserve them with try_reserve, make encode_latin1_into return Result like the UTF-16 side, make the replacement encoder's reservations in to_utf8_list_with_type_bun fallible too, and throw out-of-memory at every entry point, which errors the stream. rust-argon2 allocates the argon2 block matrix infallibly, so a memoryCost the system cannot satisfy (hash options, or the m= field of a hash passed to verify) aborted as well. Probe the same amount with a fallible reservation first and report it as OutOfMemory, which Bun.password surfaces as the PASSWORD_OUT_OF_MEMORY error it produced before the Rust port.
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Status: fixed, waiting on CI. This PR is now the
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WalkthroughThe changes make Unicode encoding, Argon2 hashing and verification, and TextEncoderStream buffer growth allocation-aware. New tests verify structured errors, stream failures, process survival, and continued operation after allocation failures. ChangesAllocation Failure Handling
Possibly related PRs
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@src/bun_core/string/immutable/unicode.rs`:
- Around line 152-156: Replace the exact reservation in the affected Unicode
decoding loop with fallible amortized reservation using try_reserve, preserving
the existing requested capacity calculation and AllocError mapping. Apply this
to the list reservation associated with utf16_remaining and keep the
WASM-specific extra calculation unchanged.
Apply the same fix in `@src/runtime/crypto/pwhash.rs` around lines 105 - 114.
Apply the same fix in `@test/js/bun/util/password.test.ts` around lines 573 - 585.
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📒 Files selected for processing (5)
src/bun_core/string/immutable/unicode.rssrc/runtime/crypto/pwhash.rssrc/runtime/webcore/TextEncoderStreamEncoder.rstest/js/bun/util/password.test.tstest/js/web/encoding/text-encoder-stream.test.ts
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Beyond the inline nit, I checked that to_utf8_list_with_type_bun has no callers outside TextEncoderStreamEncoder.rs (the signature change is fully contained), that the refactored reservation amounts in unicode.rs are unchanged ((i + count + list.len() + extra).saturating_sub(list.len()) → i + count + extra), and that ensure_total_capacity(len + N) → try_reserve(N) in the Latin-1 grow path preserves the same growth request.
Extended reasoning...
The encoder-side changes are mechanical reserve → try_reserve conversions with unchanged growth amounts, and all call sites of the newly-fallible encode_latin1_into / to_utf8_list_with_type_bun are updated. The argon2 probe is a design choice (best-effort workaround for rust-argon2's infallible vec[...]) in password-hashing code, so a maintainer look is appropriate; not approving on that basis. The scratch buffer in encodeIntoSink is correctly handled on the new error path — .take() already left an empty Vec in the RefCell, so dropping the partially-filled buf is fine.
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I reviewed this PR and didn't find any bugs; my earlier nit about .repeat() in the test was addressed in 4602d8f. Because the argon2 change adds a probe-allocation workaround in Bun.password (crypto-adjacent) rather than fixing the crate's infallible allocation directly, a human sign-off on that approach would still be worthwhile.
What was reviewed:
reserve→try_reserveswaps in the encoder andto_utf8_list_with_type_bun— growth amounts are unchanged (thelist.len()terms in the old expression cancel); the sole caller already handledAllocError.check_memory_is_allocatable—checked_mulguards overflow, probe is freed on both paths, and the recordedm=reuses the existing prescan's parser so no new grammar divergence.- The removed
VecExtimport —ensure_total_capacitywas its only use in this file. - The comment-cop and CodeRabbit threads — all addressed by follow-up commits (f41bd0d, 6b0a6cf).
Extended reasoning...
Overview
This PR restores the pre-Rust-port behavior where two JS-facing allocations sized by user input throw a JS error instead of aborting the process: TextEncoderStream's per-chunk output buffer reservations (five sites across encode_latin1_into, encode_utf16_into, and the shared to_utf8_list_with_type_bun fallback) and Bun.password's argon2 block-matrix allocation (both str_hash and str_verify). The encoder changes are mechanical reserve/reserve_exact → try_reserve/try_reserve_exact swaps with error propagation; the argon2 change adds a fallible probe reservation before delegating to rust-argon2, which allocates infallibly. Two test files gain ASAN-gated (and one Linux-release-gated) subprocess tests that exercise every reservation site.
Security risks
Bun.password is crypto-adjacent. The change does not touch what is hashed or how verification compares digests — it only inserts a fallible allocation probe before the crate's infallible one, and records m= from the existing verify prescan (same parser, same grammar). Turning a process abort into a catchable PASSWORD_OUT_OF_MEMORY error is a strict improvement DoS-wise (recoverable vs. crash). No new user-controlled parsing was introduced. The encoder changes have no security implication beyond the same abort→throw conversion.
Level of scrutiny
Moderate-to-high. The encoder half is mechanical and low-risk (restores documented Zig behavior, one shared helper whose only caller already handled the error). The argon2 half introduces a design workaround: a best-effort probe that the PR body acknowledges is TOCTOU-racy and does not help under overcommit_memory=1. The author justifies this against the alternative (patching or swapping the crate, tracked in #33153), and cites prior art in the codebase (#33014, PBKDF2.rs, scrypt). That reasoning is sound, but whether to accept a probe workaround vs. wait for/prioritize the vendoring fix is a maintainer call.
Other factors
The bug-hunting system found nothing. My earlier inline nit (test-harness .repeat convention) was addressed in 4602d8f; the CodeRabbit finding on try_reserve_exact was withdrawn after the author showed the requested amount is byte-identical to before; the comment-cop flags were addressed in f41bd0d and 6b0a6cf. Test coverage is thorough — each of the five encoder reservation sites and all four password entry points (sync/async × hash/verify) are exercised, with a post-failure sanity check that the process keeps working. I verified to_utf8_list_with_type_bun has no other callers, so its unchanged Result signature affects nothing else. The removed VecExt import was only used for the replaced ensure_total_capacity call. Given the crypto-adjacent scope and the explicit workaround design, I'm deferring rather than approving.
… lead surrogate The Bun.password change moves to its own PR. The sink-path test now sends a dangling lead surrogate ahead of each chunk, which is the case that has to be assembled in the encoder's own buffer, and covers the prepend variant of each reservation.
robobun
changed the title
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LGTM — this is the mechanical reserve → try_reserve conversion that restores the pre-port throw-OOM contract for TextEncoderStream, with per-reservation-site coverage. The one inline nit is about the stale title/description (the argon2 half was split out in 3250eb4); the code itself is fine.
Extended reasoning...
Overview
The PR now touches three files (the argon2 half was split out in 3250eb4):
src/bun_core/string/immutable/unicode.rs: tworeserve_exact→try_reserve_exactswaps into_utf8_list_with_type_bun, plus an algebraic simplification of the requested amount (thelist.len()terms in the old expression cancelled, verified in the resolved CodeRabbit thread). The function's signature was alreadyResult<_, AllocError>; this makes theErrreachable.src/runtime/webcore/TextEncoderStreamEncoder.rs:encode_latin1_intonow returnsResult<(), AllocError>like its UTF-16 sibling; everyreserve/ensure_total_capacitybecomes atry_reservemapped toAllocError; both JS-facing entry points (encode_latin1, the Latin-1 arm ofencodeIntoSink) throwRangeError: Out of memoryon failure the way the UTF-16 arms already did.encode_utf16_into's return type changes fromResult<(), ()>toResult<(), AllocError>(callers unchanged — they only test.is_err()). The now-unusedVecExtimport (which suppliedensure_total_capacity) is dropped.test/js/web/encoding/text-encoder-stream.test.ts: two ASAN-gatedtest.concurrentcases that spawn a child underallocator_may_return_null=1:max_allocation_size_mb=4and drive five inputs shaped to fail a different reservation each, once through a JS reader and once through Bun.serve's native sink.
Security risks
None. Turning a process abort on a user-sized allocation into a catchable RangeError is strictly a robustness improvement (the abort was itself a DoS vector). No new input parsing, no new trust boundaries.
Level of scrutiny
Moderate. to_utf8_list_with_type_bun is in bun_core, but I verified it has exactly one caller (TextEncoderStreamEncoder.rs:201), which already propagated via ?. The reservation amounts are unchanged from the previous code (the saturating_sub(list.len()) was a no-op). The encoder changes are the fallible variants of the same calls with the same growth amounts; the two callers that did not previously handle an error now match the two that already did. On the encodeIntoSink OOM path the taken scratch Vec is dropped rather than restored to the RefCell, which is fine (the next .take() gets a fresh empty Vec) and matches the existing > SCRATCH_CAP behaviour.
Other factors
- All prior review threads are resolved: my
.repeat→Buffer.allocnit was addressed in 4602d8f; comment-cop's comment-length complaints were addressed in f41bd0d / 6b0a6cf; CodeRabbit'stry_reservesuggestion was correctly declined (the exact reservation is behaviour-preserving and keeps peak memory lower) and withdrawn. - Tests follow harness conventions:
bunEnvspread,test.concurrent, concurrent stdout/stderr/exited drain, stdout asserted before exit code, ASAN-gated viadescribe.skipIf(!isASAN). - The one finding this run is metadata-only (title/description still describe the split-out argon2 half) — it does not affect what merges and can be fixed before the merge button is pressed.
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🟡 The PR title and roughly half the description still document the Bun.password argon2 fix (check_memory_is_allocatable, str_hash/str_verify, Error::Alloc, PASSWORD_OUT_OF_MEMORY, the ulimit repro, the password.test.ts variants), but commit 3250eb4 split that half out — the diff now touches only the three TextEncoderStream files. The title should drop "and Bun.password argon2" and the argon2 sections of the description should be removed so the PR does not overstate what it ships (CLAUDE.md #11).
Extended reasoning...
What the finding is
Commit 3250eb4 ("Split out the argon2 half; run the native-sink cases behind a carried lead surrogate") removed the src/runtime/crypto/pwhash.rs and test/js/bun/util/password.test.ts changes from this PR. The diff now contains exactly three files:
src/bun_core/string/immutable/unicode.rssrc/runtime/webcore/TextEncoderStreamEncoder.rstest/js/web/encoding/text-encoder-stream.test.ts
However, the PR metadata was not trimmed to match:
- Title: still reads "Throw out of memory from TextEncoderStream and Bun.password argon2 instead of aborting".
- Description → Problem: the second bullet (
Bun.passwordargon2:memoryCost,str_hash/str_verify, rust-argon2Memory::new, theulimit -v 4194304repro) describes code that is no longer in the diff. - Description → Fix: the
check_memory_is_allocatablebullet, the "Why a probe rather than a change to the crate" bullet, the "Not changed, deliberately: thememoryCostceiling" bullet, thepassword.test.tsverification bullet, and the second<details>block ("Bun.password without the fix") all document the split-out half. - Description → Related open PRs: crypto: accept argon2 PHC params in any order in Bun.password.verify #32314 (verify prescan) and node:crypto: implement argon2 and argon2Sync #37015 (
node:cryptoargon2) are argon2-only.
Why the timeline confirms this rather than refutes it
The timeline shows comment-cop and robobun replies on src/runtime/crypto/pwhash.rs ("Cut to two lines in f41bd0d", "Keeping these two lines: … rust-argon2 allocating the matrix infallibly in Memory::new"), which confirms pwhash.rs was in scope at commit f41bd0d and removed at 3250eb4. CodeRabbit's "Files selected for processing" for the range 293b832..3250eb4 lists only the three TextEncoderStream files. So the split is deliberate and the description is simply stale.
Step-by-step proof
git log --onelineon this branch: 293b832 (both halves), f41bd0d/6b0a6cf7/4602d8f7 (comment/test cleanups on both halves), then 3250eb4 ("Split out the argon2 half").<changed-files count="3">in the PR metadata lists onlyunicode.rs,TextEncoderStreamEncoder.rs, andtext-encoder-stream.test.ts. Neitherpwhash.rsnorpassword.test.tsappears.<title>still contains "and Bun.password argon2".- Search the description for "argon2", "pwhash", "password.test.ts", "check_memory_is_allocatable", "PASSWORD_OUT_OF_MEMORY", "ulimit -v": all present, none of it corresponds to a diff hunk.
Impact
CLAUDE.md #11: "NEVER overstate what you got done or what actually works in commits, PRs". A reader skimming the title/description (or a future git log/blame that lands on this PR) would conclude the Bun.password argon2 abort is fixed here, when it is not — that fix now lives in whatever PR the split-out half becomes. The description's "Verified" section also claims test/js/bun/util/password.test.ts (72 pass, 9 debug skips) was run for this PR, which is no longer meaningful for the current diff.
This is metadata only — merging as-is causes no runtime failure — so it is a nit, not a merge blocker.
How to fix
- Retitle to "Throw out of memory from TextEncoderStream instead of aborting" (or similar).
- Delete the argon2 bullets from Problem, Fix, Verified, and Related open PRs, and drop the second
<details>block. - Optionally note that the argon2 half was split into its own PR and link it.
2 participants
Problem
TextEncoderStreamchunk whose encoded output cannot be allocated aborts the process:memory allocation of N bytes failed, thenpanic(main thread): abort() calledand a "Bun has crashed" report. The output buffer is 1x to 3x the chunk, so for a large chunk this is where the API runs out of memory.encode_latin1_into(src/runtime/webcore/TextEncoderStreamEncoder.rs) reserves infallibly at three places (the up-front reservation, thereserve(2)retry when a two-byte char does not fit, the grow-to-fit reservation) and returns nothing.encode_utf16_intoreturns aResult, but its main reservation is infallible too, and the replacement encoder it falls back to for invalid UTF-16,to_utf8_list_with_type_bun(src/bun_core/string/immutable/unicode.rs), returnsResult<_, AllocError>while growing withreserve_exact, so itsErrwas unreachable.TextEncoderStreamEncoder.zigat the parent of 23427db, lines 68 to 169) returnedthrowOutOfMemoryValue()at each of these sites; the port lost that. strings: don't abort on UTF-8 to UTF-16 output buffer allocation failure #33014 fixed the same regression in the decoding direction (to_utf16_alloc*,TextDecoder).Fix
encode_latin1_into,encode_utf16_intoandto_utf8_list_with_type_bunis atry_reserve/try_reserve_exactmapped toAllocError. The amounts are unchanged:ensure_total_capacity(len + remain + 1)istry_reserve(remain + 1), and the oldreserve_exact((i + count + len + extra) - len)istry_reserve_exact(i + count + extra).encode_latin1_intoreturnsResultlike its UTF-16 sibling, and the two callers that did not handle an error yet (encode_latin1, and the Latin-1 arm ofTextEncoderStreamEncoder__encodeIntoSink) throw out-of-memory the wayencode_utf16and the UTF-16 arm already did.to_utf8_list_with_type_bunhas no other caller.encodeAndEnqueueinJSTextEncoderStream.cpp) already turns a pending exception into a rejected transform promise, so thewrite()rejects and the stream errors withRangeError: Out of memory; nothing else needed to change. This does not touch the abort-on-OOM policy for internal allocations; it is the same shape as strings: don't abort on UTF-8 to UTF-16 output buffer allocation failure #33014 and thetry_reservesites inencoding.rs,PBKDF2.rsandTextDecoder.test/js/web/encoding/text-encoder-stream.test.ts, two ASAN-only tests (the gate and the ASAN lanes) that run a child underallocator_may_return_null=1:max_allocation_size_mb=4. JSC allocates the input strings outside that cap, so each of five inputs makes a different encoder reservation fail: the Latin-1 up-front reservation, the Latin-1 grow-to-fit reservation, the Latin-1reserve(2)retry (an ASCII byte plus an odd number of two-byte chars leaves one spare byte), the UTF-16 simdutf-sized reservation, and the replacement encoder's first reservation (a lone surrogate ahead of N ASCII units: simdutf's N + 2 fits, 1.2N + 3 does not). One test feeds the chunks to a JS reader (write and read both reject withRangeError: Out of memory, and encoding still works afterwards); the other serves them through Bun.serve's native response sink, each behind a dangling lead surrogate so the output is assembled in the encoder's own buffer (the arm that stays the encoder's job if TextEncoderStream native-sink: write straight to the sink's write_latin1/write_utf16 #36877 hands plain chunks to the sink directly), which also covers the prepend variant of every reservation; the errored transform cancels the source with the error and the server keeps serving. Without the fix both children abort on the first input (memory allocation of 8388608 bytes failed); the per-site sizes are in the details below.bun bd test test/js/web/encoding/(577 pass),test/js/web/streams/streams.test.js,test/regression/issue/29225.test.ts,test/js/node/test/parallel/test-whatwg-webstreams-encoding.js,cargo fmt --check.Bun.passwordargon2 change; that is an unrelated allocation with its own design question and now lives in Bun.password: report an argon2 memory cost that cannot be allocated as OutOfMemory instead of aborting #39021. The same port regression exists in other user-sized buffers that are not touched here and have been handed off separately: theBun.gzipSync/gunzipSync/deflateSync/inflateSyncoutput buffers (BunObject.rs, including the one sized from the gzip trailer's ISIZE) andBun.zstdCompressSyncplus zstd decompression (BunObject.rs,zstd/lib.rs). The sinks and SQL buffers are covered by Make the allocation-only collection APIs infallible and drop the OOM wrappers around them #38888's follow-up plan.Background
Vec::try_reservereturnsErrwhen the allocator returns null, wherereservecallshandle_alloc_errorand aborts. Under ASAN the allocator is libc's, andASAN_OPTIONS=allocator_may_return_null=1:max_allocation_size_mb=Nmakes it return null for any single allocation above N MiB, which is what makes these failures reproducible; JSC allocates JS strings through its own allocator, which the cap does not apply to.AllocErroris the unit error type the crates'Errorenums wrap asAlloc(..);JSGlobalObject::throw_out_of_memory_valuesets JSC's out-of-memoryRangeErroras the pending exception.pipeThrough, cancels the stream being piped in with the same error; that cancel reason is what the native-sink test observes.TextEncoderStreamEncoder__encodeIntoSinkencodes into a reusable buffer and hands it to the sink instead of enqueueing aUint8Arrayper chunk. A lead surrogate left over from the previous chunk is encoded as a prefix of the next chunk's output, so that case always needs the encoder's buffer.Per-site aborts without the fix (debug ASAN build), each size identifying the reservation that failed
48 MiB cap, JS path:
4 MiB cap (the sizes the tests use), with the fix, ASAN's refused allocation per case; JS path then native-sink path behind a carried lead surrogate (+3 bytes of replacement prefix in each reservation):
Every case reports
{"name":"RangeError","message":"Out of memory"}and the child exits 0.[review] gate passed · iteration 0 · 3 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 1 passed · 0 rejected · iteration 0
evidence per changed file