attr, fsck: scan across embedded NUL bytes in .gitattributes by inanna-malick · Pull Request #2473 · git/git

inanna-malick · 2026-10-30T05:40:39Z

When reading a .gitattributes file from the working tree, read_attr_from_file() uses strbuf_getline(), which reads up to each '\n' regardless of embedded NUL bytes and continues parsing subsequent lines.

However, both fsck_blob() (when checking FSCK_MSG_GITATTRIBUTES_LINE_LENGTH) and read_attr_from_buf() (when reading .gitattributes from a tree or index blob) iterate with for (ptr = buf; *ptr; ) and strchrnul(ptr, '\n'), stopping early at the first embedded NUL byte. An embedded NUL on an early comment line (such as "#\0\n") therefore causes fsck_blob() and cached attribute lookups to ignore the remainder of the blob while working tree attribute lookups still parse it.

Use the known buffer size (end = buf + size and memchr(..., '\n', ...)) in both fsck_blob() and read_attr_from_buf() so that .gitattributes blobs are scanned across their full length consistently with read_attr_from_file().

Found via agent swarm driven property tests using https://recursion.wtf/posts/agents-and-property-tests/

When reading a .gitattributes file from the working tree, read_attr_from_file() uses strbuf_getline(), which reads up to each '\n' regardless of embedded NUL bytes and continues parsing subsequent lines. However, both fsck_blob() (when checking FSCK_MSG_GITATTRIBUTES_LINE_LENGTH) and read_attr_from_buf() (when reading .gitattributes from a tree or index blob) iterate with `for (ptr = buf; *ptr; )` and `strchrnul(ptr, '\n')`, stopping early at the first embedded NUL byte. An embedded NUL on an early comment line (such as "#\0\n") therefore causes fsck_blob() and cached attribute lookups to ignore the remainder of the blob while working tree attribute lookups still parse it. Use the known buffer size (`end = buf + size` and `memchr(..., '\n', ...)`) in both fsck_blob() and read_attr_from_buf() so that .gitattributes blobs are scanned across their full length consistently with read_attr_from_file(). Found via agent swarm driven property tests using https://recursion.wtf/posts/agents-and-property-tests/ Signed-off-by: Inanna Malick <inanna@recursion.wtf>

gitgitgadget-git · 2026-10-30T05:41:30Z

Welcome to GitGitGadget

Hi @inanna-malick, and welcome to GitGitGadget, the GitHub App to send patch series to the Git mailing list from GitHub Pull Requests.

Please make sure that either:

Your Pull Request has a good description, if it consists of multiple commits, as it will be used as cover letter.
Your Pull Request description is empty, if it consists of a single commit, as the commit message should be descriptive enough by itself.

You can CC potential reviewers by adding a footer to the PR description with the following syntax:

CC: Revi Ewer <revi.ewer@example.com>, Ill Takalook <ill.takalook@example.net>

NOTE: DO NOT copy/paste your CC list from a previous GGG PR's description,
because it will result in a malformed CC list on the mailing list. See
example.

Also, it is a good idea to review the commit messages one last time, as the Git project expects them in a quite specific form:

the lines should not exceed 76 columns,
the first line should be like a header and typically start with a prefix like "tests:" or "revisions:" to state which subsystem the change is about, and
the commit messages' body should be describing the "why?" of the change.
Finally, the commit messages should end in a Signed-off-by: line matching the commits' author.

It is in general a good idea to await the automated test ("Checks") in this Pull Request before contributing the patches, e.g. to avoid trivial issues such as unportable code.

Contributing the patches

Before you can contribute the patches, your GitHub username needs to be added to the list of permitted users. Any already-permitted user can do that, by adding a comment to your PR of the form /allow. A good way to find other contributors is to locate recent pull requests where someone has been /allowed:

Search: is:pr is:open "/allow"

Both the person who commented /allow and the PR author are able to /allow you.

An alternative is the channel #git-devel on the Libera Chat IRC network:

<newcontributor> I've just created my first PR, could someone please /allow me? https://github.com/gitgitgadget/git/pull/12345
<veteran> newcontributor: it is done
<newcontributor> thanks!

Once on the list of permitted usernames, you can contribute the patches to the Git mailing list by adding a PR comment /submit.

If you want to see what email(s) would be sent for a /submit request, add a PR comment /preview to have the email(s) sent to you. You must have a public GitHub email address for this. Note that any reviewers CC'd via the list in the PR description will not actually be sent emails.

After you submit, GitGitGadget will respond with another comment that contains the link to the cover letter mail in the Git mailing list archive. Please make sure to monitor the discussion in that thread and to address comments and suggestions (while the comments and suggestions will be mirrored into the PR by GitGitGadget, you will still want to reply via mail).

If you do not want to subscribe to the Git mailing list just to be able to respond to a mail, you can download the mbox from the Git mailing list archive (click the (raw) link), then import it into your mail program. If you use GMail, you can do this via:

curl -g --user "<EMailAddress>:<Password>" \
    --url "imaps://imap.gmail.com/INBOX" -T /path/to/raw.txt

To iterate on your change, i.e. send a revised patch or patch series, you will first want to (force-)push to the same branch. You probably also want to modify your Pull Request description (or title). It is a good idea to summarize the revision by adding something like this to the cover letter (read: by editing the first comment on the PR, i.e. the PR description):

Changes since v1:
- Fixed a typo in the commit message (found by ...)
- Added a code comment to ... as suggested by ...
...

To send a new iteration, just add another PR comment with the contents: /submit.

Need help?

New contributors who want advice are encouraged to join git-mentoring@googlegroups.com, where volunteers who regularly contribute to Git are willing to answer newbie questions, give advice, or otherwise provide mentoring to interested contributors. You must join in order to post or view messages, but anyone can join.

You may also be able to find help in real time in the developer IRC channel, #git-devel on Libera Chat. Remember that IRC does not support offline messaging, so if you send someone a private message and log out, they cannot respond to you. The scrollback of #git-devel is archived, though.

Copilot

🟡 Changes recommended

Regression coverage is missing for embedded-NUL handling in fsck and attribute lookups, so existing tests would still pass if the fixes were reverted.

2 open issues

What changed in this PR

This PR makes .gitattributes blob scanning continue past embedded NUL bytes, aligning tree and index attribute lookups with working-tree behavior and preventing fsck from skipping later oversized lines.

Changes:

Replace NUL-terminated traversal with size-bounded newline searches in both scanners.
Handle final lines without a trailing newline.

File	Description
`fsck.c`	Check attribute line lengths across the full blob, including content after embedded NULs.
`attr.c`	Continue parsing tree and index attribute rules after lines containing embedded NULs.

_{Review effort: Balanced}

+	end = buf + length;
+	for (sp = buf; sp < end;) {


+		for (ptr = buf; ptr < end; ) {
+			const char *eol = memchr(ptr, '\n', end - ptr);


Copilot AI balanced review requested due to automatic review settings October 30, 2026 05:40

github-project-automation Bot added this to Op-Amp Frequency Response and Applications Suite Oct 30, 2026

github-project-automation Bot moved this to Todo in Op-Amp Frequency Response and Applications Suite Oct 30, 2026

Copilot started reviewing on behalf of inanna-malick October 30, 2026 05:41

View session

gitgitgadget-git Bot added the new user label Oct 30, 2026

Copilot AI reviewed Oct 30, 2026

View reviewed changes

Comment thread attr.c

Comment on lines +751 to +752

end = buf + length;

for (sp = buf; sp < end;) {

Comment thread fsck.c

Comment on lines +1239 to +1240

for (ptr = buf; ptr < end; ) {

const char *eol = memchr(ptr, '\n', end - ptr);

Navigation Menu

Repository navigation

attr, fsck: scan across embedded NUL bytes in .gitattributes - #2473

attr, fsck: scan across embedded NUL bytes in .gitattributes#2473
inanna-malick wants to merge 1 commit into
git:masterfrom
inanna-malick:fix/attr-and-fsck-embedded-nul-handling

inanna-malick commented Oct 30, 2026

Uh oh!

gitgitgadget-git Bot commented Oct 30, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

This branch has not been deployed

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

		for (ptr = buf; ptr < end; ) {
		const char *eol = memchr(ptr, '\n', end - ptr);

Conversation

inanna-malick commented Oct 30, 2026

Uh oh!

gitgitgadget-git Bot commented Oct 30, 2026

Welcome to GitGitGadget

Contributing the patches

Need help?

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Uh oh!

This branch has not been deployed

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants