Reject paths with embedded null bytes in Bun.mmap, unix sockets, and bun:sqlite

[dylan-conway]

What does this PR do?

Bun.mmap("/tmp/a\0b") aborted the whole process (panic: ZStr::as_cstr: interior NUL would truncate the C view) instead of throwing. Bun.mmap now runs the same null-byte validation as fs.* / Bun.file and throws ERR_INVALID_ARG_VALUE ("must be a string, Uint8Array, or URL without null bytes").

A few other path-taking entry points accepted an embedded null byte and silently truncated at it, so they bound/opened a different path than the caller asked for:

• Unix socket paths — Bun.serve({ unix }), Bun.listen/Bun.connect({ unix }), net.Server#listen(path), net.connect(path). "/tmp/u\0nix" bound /tmp/u. These now fail with EINVAL, matching Node/libuv (uv_pipe_bind2/uv_pipe_connect2). Linux abstract-namespace names (leading \0) are still allowed and may contain nulls throughout, as in libuv. The node:cluster SCHED_NONE unix bind, which builds its own sockaddr_un in the primary, gets the same check.
• bun:sqlite new Database("/tmp/a\0b.sqlite") created /tmp/a; db.loadExtension(name) and Database.setCustomSQLite(path) handed a truncated path to dlopen. All three now throw ERR_INVALID_ARG_VALUE.

Checked and left alone: new Worker(path), Bun.build({ entrypoints }), and import() with a null byte already fail cleanly with ModuleNotFound (the resolver matches directory entries, so nothing is truncated), which lines up with Node's async error event for Worker.

How did you verify your code works?

Added tests next to the existing coverage in mmap.test.js, serve-listen.test.ts (serve/listen/connect), node-net-server.test.ts, cluster.test.ts, and sqlite.test.js. Each fails with USE_SYSTEM_BUN=1 (abort / no throw / truncated socket or db file created) and passes with bun bd test <file>; the full files and test/js/bun/net/unix-socket-unlink.test.ts (abstract sockets) also pass on the debug build. Also drove the debug binary directly with each repro and confirmed the process keeps running and no truncated file/socket appears on disk.

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 05bfeb33-e160-430b-a24e-17c3bc867497

📥 Commits

Reviewing files that changed from the base of the PR and between 9ee60cb and 27a6f46.

📒 Files selected for processing (9)

• packages/bun-usockets/src/bsd.c
• src/js/bun/sqlite.ts
• src/runtime/api/BunObject.rs
• src/runtime/node/node_cluster_binding.rs
• test/js/bun/http/serve-listen.test.ts
• test/js/bun/sqlite/sqlite.test.js
• test/js/bun/util/mmap.test.js
• test/js/node/cluster.test.ts
• test/js/node/net/node-net-server.test.ts

Walkthrough

The changes add embedded-NUL validation to Unix socket, SQLite, and Bun.mmap paths. Linux abstract socket names remain supported. Tests verify error codes, messages, truncated-path protection, and platform-specific behavior.

Changes

Embedded NUL validation

Layer / File(s)	Summary
Unix socket path validation packages/bun-usockets/src/bsd.c, src/runtime/node/node_cluster_binding.rs, test/js/bun/http/serve-listen.test.ts, test/js/node/cluster.test.ts, test/js/node/net/node-net-server.test.ts	Unix socket paths with embedded NUL bytes now return EINVAL, except Linux abstract socket names beginning with NUL. Tests cover Bun.serve, Bun.listen, cluster binding, and Node server listening.
SQLite path validation src/js/bun/sqlite.ts, test/js/bun/sqlite/sqlite.test.js	Database filenames, extension names, and custom SQLite paths now reject embedded NUL bytes with $ERR_INVALID_ARG_VALUE. Tests verify messages and prevent truncated files.
Memory-mapping path validation src/runtime/api/BunObject.rs, test/js/bun/util/mmap.test.js	Bun.mmap now rejects paths containing embedded NUL bytes before path resolution. The test verifies the error code, message, and catchable subprocess behavior.

🚥 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 and concisely summarizes the main change across mmap, Unix sockets, and bun:sqlite.
Description check	✅ Passed	The description completes both required sections and clearly documents the changes, affected APIs, validation behavior, and verification steps.

---

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[robobun]

^{Updated 1:05 PM PT - Aug 14th, 2026}

✅ @dylan-conway, your commit 6177087c00d5502e050417442fe1fe78c3211a09 passed in Build #96125! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 38514

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bun-38514 --bun

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Actionable comments posted: 1

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Inline comments:
In `@test/js/node/cluster.test.ts`:
- Around line 294-305: Update the worker exit handler in the cluster test to
assign the worker’s exit code to process.exitCode instead of forcing
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---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: d22ecc30-87cc-4855-92cf-dffeb53cd2cc

📥 Commits

Reviewing files that changed from the base of the PR and between 7cf6296 and a306595.

📒 Files selected for processing (9)

• packages/bun-usockets/src/bsd.c
• src/js/bun/sqlite.ts
• src/runtime/api/BunObject.rs
• src/runtime/node/node_cluster_binding.rs
• test/js/bun/http/serve-listen.test.ts
• test/js/bun/sqlite/sqlite.test.js
• test/js/bun/util/mmap.test.js
• test/js/node/cluster.test.ts
• test/js/node/net/node-net-server.test.ts

[claude]

LGTM — the follow-up commits addressed all four earlier findings (cluster SCHED_NONE bind, sqlite loadExtension/setCustomSQLite, Bun.connect test coverage, and the shared-tmpdir hermeticity in node-net-server.test.ts).

What was reviewed:

• bsd_create_unix_socket_address: NUL check placed after the empty-path guard so path[0] is safe, Linux abstract-namespace exemption matches libuv, and both listen/connect callers route through it.
• cluster_raw_bind and Bun.mmap reuse the existing contains_char / Valid::path_null_bytes helpers; sqlite guards use $ERR_INVALID_ARG_VALUE consistently.
• Tests now each use an isolated temp dir and assert both the error code and that no truncated file/socket appears; the cluster test propagates the worker exit code.

Extended reasoning...

Overview

Adds embedded-NUL validation to five path-taking entry points that previously either aborted (Bun.mmap) or silently truncated at the NUL and operated on the wrong path (unix sockets via bsd_create_unix_socket_address, the cluster SCHED_NONE raw bind, and three bun:sqlite path arguments). Production changes total ~20 lines across bsd.c, BunObject.rs, node_cluster_binding.rs, and sqlite.ts; the remaining five files are tests.

Security risks

None introduced. This is hardening: it closes a path-truncation footgun where "/tmp/a\0b" would bind/open /tmp/a. The Linux abstract-namespace exemption (leading NUL, length-delimited) is preserved in both bsd.c and node_cluster_binding.rs, matching libuv's uv_pipe_bind2 semantics, so no valid input is newly rejected.

Level of scrutiny

Low-to-medium. Each change is a small guard clause inserted before the existing path-handling logic, using in-tree helpers (Valid::path_null_bytes, bun_core::strings::contains_char, memchr, $ERR_INVALID_ARG_VALUE) rather than bespoke checks. The bsd.c check is placed after the path_len == 0 early return so the path[0] dereference is safe, and before any of the long-path dirfd workarounds so those never see a NUL-containing path. No API surface or default behavior changes for valid inputs.

Other factors

Three rounds of prior automated review left four findings (missing sibling sites in cluster and sqlite, missing connect-side test coverage, non-hermetic tmpdir in the net test, and the CodeRabbit note on masking worker exit codes). All were addressed in commits a306595, 28ba8b8, and 6177087, and every thread is marked resolved. Test coverage now spans serve/listen/connect, net.Server, cluster SCHED_NONE, sqlite open/loadExtension/setCustomSQLite, and mmap — each in an isolated temp directory with both the error code and the negative contract (no truncated artifact on disk) asserted.

[claude]

LGTM — all prior review feedback has been addressed, CI is green, and this run found no new issues.

What was reviewed:

• The NUL check in bsd_create_unix_socket_address correctly exempts Linux abstract-namespace names and sets errno/WSA before the early return; both listen and connect callers reach it.
• cluster_raw_bind's hand-built sockaddr_un now has the same guard with the same abstract exemption; the check runs before any fd is created.
• Bun.mmap reuses the existing Valid::path_null_bytes helper (same error shape as fs.*); the sqlite guards throw before SQL.open/setCustomSQLite so no global state is touched on the error path.
• Tests use isolated temp dirs and assert both the error code and that no truncated file/socket is created.

Extended reasoning...

Overview

This PR adds embedded-NUL-byte validation to five path-taking entry points that previously either aborted (Bun.mmap) or silently truncated at the NUL and operated on the wrong path (unix sockets via Bun.serve/Bun.listen/Bun.connect/net.Server#listen, cluster SCHED_NONE bind, and bun:sqlite's Database constructor / loadExtension / setCustomSQLite). Source changes span bsd.c (16 lines), BunObject.rs (1 line), node_cluster_binding.rs (4 lines), and sqlite.ts (9 lines), plus tests in five files.

Security risks

None introduced; this is security-positive hardening that directly implements REVIEW.md's "Reject embedded NULs in strings passed to C APIs." The Linux abstract-namespace exemption (leading NUL, may contain NULs throughout) is preserved in both bsd.c and node_cluster_binding.rs, matching libuv's uv_pipe_bind2 semantics, so no legitimate abstract-socket usage is broken.

Level of scrutiny

Medium. The changes are mechanical validation guards following established in-tree patterns ($ERR_INVALID_ARG_VALUE, node::types::Valid::path_null_bytes, errno = EINVAL), each placed before any allocation or side effect. The bsd.c check runs before *addrlen is written and before any fd is opened; the cluster check runs before libc::socket; the sqlite checks run before initializeSQL() / SQL.open, so the error path leaves no partial state.

Other factors

This PR has been through two rounds of review: my earlier run flagged the missing cluster_raw_bind sibling, the missing loadExtension/setCustomSQLite guards, missing Bun.connect test coverage, and a shared-tmpdir hermeticity issue in node-net-server.test.ts — all four were fixed and are verified present in the current diff. CodeRabbit's note about the cluster test masking worker exit codes was also addressed (process.exit(code ?? 1) + exitCode assertion). CI passed on the latest commit (Build #96125). Every source change has a corresponding test that asserts both the specific error code/message and that no truncated artifact is left on disk.

[robobun]

#37002 carried the same bsd_create_unix_socket_address guard and is now closed in favor of this PR.

To check the overlap, I built this branch on top of current main (d393bf9) and ran the test file from #37002 against it. Only test/js/bun/http/serve-listen.test.ts conflicts with main: both sides add a test at the same spot. Every surface from #37002 already rejects the path here with EINVAL from the C layer, with no truncated socket file and no connection to the prefix path: Bun.connect, Bun.listen, Bun.serve, fetch({ unix }), net.connect, net.Server#listen, http.request({ socketPath }), http.Server#listen, and a trailing NUL. Linux abstract names with an interior NUL still round trip.

Parts of #37002 that are not in this PR, in case you want to fold any of them in:

• fetch("http://h/", { unix: "a\0b" }) rejects here, but with the generic FailedToOpenSocket TypeError ("Was there a typo in the url or port?"). Reject unix socket paths containing interior NUL bytes #37002 threw "unix" must not contain null bytes from src/runtime/webcore/fetch.rs before the request left the JS thread. fetch: anchor a relative unix socket path to the cwd at call time #40982 (on main) added absolute_unix_socket_path in fetch.rs with the leading-NUL abstract-name check. A fetch-level check should share that helper.
• Synchronous argument errors for Bun.connect / Bun.listen (src/runtime/socket/Handlers.rs) and Bun.serve (src/runtime/server/ServerConfig.rs), next to the existing "hostname" must not contain null bytes check. Here they report EINVAL with Failed to connect / Failed to listen at <path> / EINVAL: invalid argument, listen '<path>'.
• A JS-side UV_EINVAL check in src/js/node/net.ts, so node:net does not reach the native connect or listen. Not needed for the behavior: net.connect and net.Server#listen already produce Node's exact messages here (connect EINVAL <path> and listen EINVAL: invalid argument <path>).
• The test file test/js/bun/net/unix-socket-nul-byte.test.ts: a decoy listener at the truncated prefix path that must receive no connection, checked across all of the surfaces above, plus abstract-name round trips with an interior NUL.