apply: fix header bounds check, empty image removal, and binary hunk leak by inanna-malick · Pull Request #2476 · git/git

inanna-malick · 2026-10-30T05:45:41Z

Fix three memory safety issues in apply.c:

In git_header_name(), check (second - name) + len <= line_len before reading second[len]. When the postimage path after b/ is shorter than the preimage path a/<name>, second[len] previously indexed past the end of the diff --git line (and past the end of the patch buffer if the header was near EOF).
In image_remove_first_line() and image_remove_last_line(), guard against !img->line_nr before indexing img->line or decrementing img->line_nr. When a hunk contains an empty context line (\n) followed by \ No newline at end of file, parse_fragment() counts it in leading/trailing, whereas apply_one_fragment() skips it (plen < 0). Context reduction under -C0 can then call image_remove_first_line() or image_remove_last_line() on an empty preimage or postimage (line == NULL, line_nr == 0).
In parse_binary_hunk(), free(frag) when inflate_it() fails so the struct fragment allocation is not leaked on the corrupt: error path.

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

…leak Fix three memory safety issues in apply.c: 1. In git_header_name(), check `(second - name) + len <= line_len` before reading `second[len]`. When the postimage path after `b/` is shorter than the preimage path `a/<name>`, `second[len]` previously indexed past the end of the `diff --git` line (and past the end of the patch buffer if the header was near EOF). 2. In image_remove_first_line() and image_remove_last_line(), guard against `!img->line_nr` before indexing `img->line` or decrementing `img->line_nr`. When a hunk contains an empty context line (`\n`) followed by `\ No newline at end of file`, `parse_fragment()` counts it in `leading`/`trailing`, whereas `apply_one_fragment()` skips it (`plen < 0`). Context reduction under `-C0` can then call `image_remove_first_line()` or `image_remove_last_line()` on an empty `preimage` or `postimage` (`line == NULL`, `line_nr == 0`). 3. In parse_binary_hunk(), `free(frag)` when `inflate_it()` fails so the `struct fragment` allocation is not leaked on the `corrupt:` error path. 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 · 2026-10-30T05:46:14Z

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🟡 Changes recommended

The new bounds and context-reduction guards lack regression tests for malformed pathname headers and empty-image reduction under -C0, leaving the original out-of-bounds read and crash scenarios untested.

2 open issues

What changed in this PR

This PR addresses three memory-safety issues in Git’s patch application code.

Changes:

Bounds-checks the postimage pathname before reading its newline terminator.
Makes first- and last-line removal safe for empty images during context reduction.
Frees the binary-hunk fragment when decompression fails.

File	Description
`apply.c`	Adds pathname bounds checking, empty-image guards, and cleanup on binary-hunk decompression failure.

_{Review effort: Balanced}

+	if (!img->line_nr)
+		return;


+			if ((second - name) + len <= line_len &&
+			    second[len] == '\n' && !strncmp(name, second, len))


Copilot AI balanced review requested due to automatic review settings October 30, 2026 05:45

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 05:46

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

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Comment thread apply.c

Comment on lines +369 to +370

if (!img->line_nr)

return;

Comment thread apply.c

Comment on lines +1343 to +1344

if ((second - name) + len <= line_len &&

second[len] == '\n' && !strncmp(name, second, len))

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apply: fix header bounds check, empty image removal, and binary hunk leak - #2476

apply: fix header bounds check, empty image removal, and binary hunk leak#2476
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		if ((second - name) + len <= line_len &&
		second[len] == '\n' && !strncmp(name, second, len))

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inanna-malick commented Oct 30, 2026

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