shell(mkdir, touch): report operands longer than the path buffers instead of aborting - #38379
shell(mkdir, touch): report operands longer than the path buffers instead of aborting#38379robobun wants to merge 7 commits into
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…tead of aborting A relative mkdir operand was joined onto the cwd in the 4096-byte thread-local join buffer and every touch operand into a stack PathBuffer, so an operand longer than that aborted the process. Join through the spill variant instead. mkdir also reports ENAMETOOLONG itself for a result that does not fit a PathBuffer, since the node:fs mkdir it calls assumes the bound its JS entry points enforce and otherwise operates on "" and reports ENOENT; touch passes the path to the OS whole, which reports ENAMETOOLONG for it.
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Updated 6:52 AM PT - Aug 14th, 2026
✅ @robobun, your commit cdf41563992692bacb8945ce1cfe4de402663923 passed in 🧪 To try this PR locally: bunx bun-pr 38379That installs a local version of the PR into your bun-38379 --bun |
WalkthroughChangesThe shell Shell path handling
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Inline comments:
In `@test/js/bun/shell/commands/mkdir.test.ts`:
- Around line 33-34: Update the existsSync assertions in
test/js/bun/shell/commands/mkdir.test.ts lines 33-34 and
test/js/bun/shell/commands/touch.test.ts lines 31-32 to construct absolute paths
from process.cwd() for “short” and “normalized”.
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src/runtime/shell/builtin/mkdir.rssrc/runtime/shell/builtin/touch.rstest/js/bun/shell/commands/mkdir.test.tstest/js/bun/shell/commands/touch.test.ts
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Review feedback so far is addressed: ed5c902 makes the fixtures assert on absolute paths (and drops the duplicate checks on the parent side), 6f25f02 cuts the two explanatory comments in mkdir.rs and touch.rs down to one line each; the reasoning behind mkdir's own ENAMETOOLONG check is in the description above. No behavior change in either commit; both test files still fail on the released build and pass with this branch. |
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Status: the review feedback is handled. ed5c902 makes the fixtures check absolute paths, 6f25f02 trims the two code comments to one line each, and 6e9136b adds the absolute |
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LGTM — focused crash-to-error fix using the established join_z_spill helper, with subprocess-isolated tests covering the variant matrix.
On my earlier note about the mkdir absolute branch not normalizing before the length check: the absoluteDotSlashes case in mkdir.test.ts pins that as intentional (matches coreutils/kernel; lexical normalization of .. through a symlink diverges from kernel resolution), which is a sound rationale — happy to leave it as-is.
Extended reasoning...
Overview
The PR replaces fixed-buffer path joins in two shell builtin worker functions with the spill-capable variant. ShellMkdirTask::run_from_thread_pool (mkdir.rs) swaps resolve_path::join_z for join_z_spill on the relative-operand branch and adds an explicit >= MAX_PATH_BYTES → ENAMETOOLONG guard before handing the path to NodeFS (which otherwise silently truncates to "" via PathLike::slice_z and reports ENOENT). ShellTouchTask::run_from_thread_pool (touch.rs) swaps join_z_buf into a stack PathBuffer for join_z_spill on both branches, letting the OS report ENAMETOOLONG naturally and dropping a large stack allocation. Two new test files run each builtin in a child process against 5000-byte and 100000-byte operands (relative, absolute, -p, mixed with a valid operand, and a 6000-byte ./ spelling that normalizes short).
Security risks
None introduced; the change is strictly a hardening. A user-reachable panic (out-of-bounds slice write in normalize_string_generic_tz) on adversarial operand length becomes a catchable exit-1 error. No new parsing, no new trust boundaries, no path-traversal surface added — the joined path is passed to the same NodeFS::mkdir_* / bun_sys::utimens/open calls as before.
Level of scrutiny
Medium-low. The Rust change is ~15 net lines across two worker functions, swapping one in-tree join helper for its documented spill variant (already used by GlobWalker and slated for the sibling rm/mv/cp PRs) plus one length check whose bound and rationale are named in the comment (Valid::path_string_length). No control-flow, ownership, or threading changes. The tests are the larger half of the diff and follow harness conventions closely (subprocess isolation, tempDir, concurrent pipe drain, exact stderr assertion on POSIX with a per-operand-fails relaxation on Windows, Buffer.alloc over .repeat).
Other factors
My previous inline comment (mkdir's absolute branch bounds the as-written length rather than the normalized one) was nit-level and self-noted as not a regression and matching coreutils; the absoluteDotSlashes test case pins this behavior with a comment giving the symlink-semantics rationale, which resolves it. All earlier bot threads (comment-cop, coderabbit absolute-path assertion) are addressed and marked resolved. The PR description documents USE_SYSTEM_BUN=1 failure and debug-build pass, and the related shell-builtin PRs it names use the same pattern.
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Review has converged: the mkdir.rs note above is withdrawn on the strength of the absoluteDotSlashes case, and every thread is resolved. No further changes planned; ready for a maintainer once CI reports. |
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Inline comments:
In `@test/js/bun/shell/commands/mkdir.test.ts`:
- Line 71: Update the absoluteDotSlashes expectation in the mkdir test to assert
the normalized Windows success result, using exitCode 0, empty stderr, and
created true instead of expect.anything(); preserve the existing non-Windows
failure expectation.
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LGTM — my earlier note on the absolute-operand branch is addressed: 6e9136b pins the as-written bounding with absoluteDotSlashes, and the symlink-.. rationale for not normalizing absolute operands is sound.
Extended reasoning...
Overview
Crash fix in two shell builtins. ShellMkdirTask::run_from_thread_pool and ShellTouchTask::run_from_thread_pool swap the fixed-buffer join_z/join_z_buf for the spill variant join_z_spill (already defined in src/paths/resolve_path.rs:1445 and used by the sibling rm/cp/mv fixes), so a user-supplied operand longer than MAX_PATH_BYTES no longer indexes past the buffer and panics the process. mkdir additionally enforces the Valid::path_string_length bound the node:fs layer assumes, so an over-long path reports ENAMETOOLONG instead of ENOENT-on-"". Two new test files under test/js/bun/shell/commands/ spawn a child bun and cover relative/absolute/-p/100k-byte/mixed-operand/./-normalization cases on all platforms.
Security risks
None new. The change replaces an unchecked write into a fixed thread-local buffer with a heap-spilling variant on user-controlled input — strictly a hardening. No new syscalls, no privilege changes; the ENAMETOOLONG path just constructs a bun_sys::Error and returns.
Level of scrutiny
Moderate. The Rust diff is ~15 net lines across two worker-pool functions and is a mechanical helper swap plus one length guard; the surrounding task lifecycle, error plumbing, and OutputTask machinery are untouched. The test files are the bulk of the diff and follow the established commands/<builtin>.test.ts pattern (child process, tempDir, drained pipes, one combined toEqual).
Other factors
- My prior review flagged that the absolute mkdir branch bounds the operand as written rather than normalized. The author kept it deliberately (normalizing would change
..-through-symlink semantics, which is out of scope for a crash fix and matches coreutils/kernel behaviour), addedabsoluteDotSlashesto pin it, and corrected the description. That resolution is reasonable. - CodeRabbit's absolute-path nit and the comment-cop notes were addressed in ed5c902 and 6f25f02; all threads resolved.
- Tests assert exact stderr on POSIX and
expect.stringMatching(/^mkdir: /)on Windows where the errno is OS-chosen — appropriate branching, not precision loss. - Verified
join_z_spillexists atresolve_path.rs:1445;process.argv[1]underbun -eis the first extra arg, so the fixture receives the tempdir correctly.
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Ready for a maintainer. Final state: mkdir and touch join through join_z_spill, mkdir reports ENAMETOOLONG itself for results that do not fit a PathBuffer (relative operands on the normalized path, absolute ones as written, both pinned by the tests), and the Windows expectations were checked on a Windows machine (details in the description). Review threads are all resolved, including the normalization question on mkdir.rs. CI: the two new test files pass on every lane in builds 95567, the retrigger, and 95737 (head cdf4156); the lanes those builds report as failed are retry-passed flakes in unrelated files (child_process IPC, require-cache leak check, napi buffer, s3, solc, cluster tests), plus the bake deinitialization Windows crash in 95567, which was reported separately. No further pushes planned from my side. |
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Problem
Bun.$mkdir <operand>with a relative operand longer than the join buffer, andtouch <operand>with any operand longer than a path buffer, abort the process:panic: range end index 5004 out of range for slice of length 4094(cwd/tmp, 5000-byte operand; same formkdir -pand for an absolutetouchoperand).mkdirwith an absolute operand that does not fit a path buffer reports the wrong error:mkdir: /aaa...: No such file or directoryinstead ofFile name too long.ShellMkdirTask::run_from_thread_pool(src/runtime/shell/builtin/mkdir.rs) joins a relative operand onto the cwd withresolve_path::join_z, which writes into a fixed 4096-byte thread-local buffer;ShellTouchTask::run_from_thread_pool(touch.rs) joins both kinds of operand withjoin_z_bufinto a stackPathBuffer. Neither join bounds-checks its output (normalize_string_generic_tzinsrc/paths/resolve_path.rs), and the operand comes straight from the user.PathLike. For JS callers,Valid::path_string_length(src/runtime/node/types.rs) rejects paths ofMAX_PATH_BYTESor more up front; for anything longer,PathLike::slice_zreturns""andmkdir("")fails with ENOENT. The shell builds thePathLikeitself and skipped that check.Fix
join_z_spill, the existing variant that falls back to a caller-ownedVecwhen the parts would not fit (the same helperfs.readdir,Bun.Globand the openrmfix shell(rm): stop panicking on operands longer than the path scratch buffers #37521 use). The result is the same normalized path as before for every operand that used to work.mkdirthen reportsENAMETOOLONGitself, naming the path, when the path it is about to create isMAX_PATH_BYTESor longer, i.e. the bound node:fs assumes. For a relative operand that is the joined, normalized path, so a long././.../xspelling is still created; an absolute operand is passed on as written (as before: normalizing it would change what..means across a symlink), so it is bounded as written, which is also what the kernel and coreutils do with such an operand. Both cases are in the test.touchneeds no check of its own: it callsbun_sys::utimens/openwith the string as is, and the OS reportsENAMETOOLONGfor it like for any other operand. It also no longer puts aPathBufferon the worker's stack (about 96 KB on Windows).test/js/bun/shell/commands/mkdir.test.tsandtouch.test.ts(thecommands/directory has one file per builtin; these two had none). Each runs the builtin in a child bun and covers a 5000-byte relative and absolute operand,mkdir -p, a 100000-byte operand (longer than the buffer on Windows too), a long operand next to a normal one that must still be created, and a 6000-byte./spelling that must still succeed (for mkdir also the absolute form of it, which must be refused as written; POSIX only, since on Windows it fits the buffer).USE_SYSTEM_BUN=1 bun test test/js/bun/shell/commands/mkdir.test.ts test/js/bun/shell/commands/touch.test.ts: both fail, the child aborts with the panic above. Without the new mkdir check, the mkdir cases fail on the ENOENT message instead.bun bd test test/js/bun/shell/commands/mkdir.test.ts test/js/bun/shell/commands/touch.test.ts: pass.bunshell.test.ts,file-io.test.ts,commands/rm.test.tspass as well;cargo checkfor the Windows and macOS targets is clean.mkdiroperand there too (the join buffer is 4096 bytes on every platform), and creates the directory for the absolute././.../xspelling (the branch this change does not touch below 98302 bytes), which is what the Windows side of the test asserts; both checked on a Windows x64 machine. The Windows lanes of this PR's CI runs pass both test files.rm(shell(rm): stop panicking on operands longer than the path scratch buffers #37521),mv(shell(mv): report ENAMETOOLONG instead of panicking when a source name does not fit the path buffers #37527) andcp(shell(cp): report ENAMETOOLONG instead of panicking on operands longer than the path buffers #38162) fix the same pattern in their builtins; shell(cp): report ENAMETOOLONG instead of panicking on operands longer than the path buffers #38162 addsshell_join_pathhelpers ininterpreter.rsthat touch could switch to in one line once either PR lands. shell: fail an empty operand with ENOENT instead of acting on the cwd #38002 (empty operands) also createscommands/mkdir.test.tsandtouch.test.ts; whichever lands second appends its test to the other's file.ls -Rjoins real directory entries through the same thread-local buffer, but that needs an on-disk tree within PATH_MAX whose entries join past 4096 bytes rather than a long operand, and is left alone here.Background
mkdirandtouchschedule one task per operand on the worker pool. A task either succeeds or stores abun_sys::Error, which the builtin prints as<cmd>: <path>: <coreutils message>and turns into exit code 1 once every task has finished, so one failing operand does not stop the others.$.cwd(),cd), which can differ from the process cwd, so these builtins make relative operands absolute by joining them onto the shell cwd as strings before calling an implementation that takes a path.resolve_path::join_zandjoin_z_bufconcatenate and normalize their parts (.,.., repeated separators) into a fixed buffer without checking that the result fits; the*_spillvariants take aVecto grow into when the unnormalized length would not fit, and otherwise behave identically.PathBufferis[u8; MAX_PATH_BYTES]: 4096 bytes on Linux, 1024 on macOS, 98302 on Windows. The node:fs layer copies every path it receives into one, which is why its JS entry points reject longer paths before calling it.no test proof · iteration 0 · Platform-specific test(s) that do not run on this machine. Deferring to CI, which covers all platforms: test/js/bun/shell/commands/mkdir.test.ts test/js/bun/shell/commands/touch.test.ts