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apply: avoid leaking abandoned git-header state

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When find_header() sees a "diff --git" line, it calls
parse_git_diff_header() to parse the git-style extended header. That parser
updates the caller's struct patch as it goes, filling in the default name,
old/new names, and new/delete state.

But not every "diff --git" line found while scanning is ultimately accepted
as the patch header. If parse_git_diff_header() returns a length that covers
only the "diff --git" line, find_header() continues scanning for another
header. In that case the partially parsed git-header state must not interfere
with the later traditional "---" / "+++" header.

Leaving that state behind can combine incompatible metadata from the
abandoned git header and the later traditional header. For example, after:

	diff --git a/foo b/foo

	--- /dev/null
	+++ b/foo
	@@ -0,0 +1 @@
	+x

the abandoned git header can leave an old name in the patch, while the
traditional header marks the patch as creating a new file. That impossible
state later trips the check_preimage() assertion that a creation patch should
not have a preimage.

Parse a candidate git header into a temporary patch and line number. Commit
that temporary state to the real patch only when the git header is actually
accepted; otherwise release it and keep scanning with the original patch
state unchanged.

Also reject an empty parsed default name from the "diff --git" line.
An empty patch->def_name is not a valid pathname, and should not be
used later as a fallback when old_name and new_name are missing.

Add regression tests for both the empty default-name case and the non-empty
abandoned-header case above.

Co-authored-by: Mahya SamDaliri <ms3539@njit.edu>
Signed-off-by: Mahya SamDaliri <ms3539@njit.edu>
Co-authored-by: Haotian Zhang <haotian.zhang@njit.edu>
Signed-off-by: Haotian Zhang <haotian.zhang@njit.edu>
Co-authored-by: Martin Kellogg <martin.kellogg@njit.edu>
Signed-off-by: Martin Kellogg <martin.kellogg@njit.edu>
Signed-off-by: Zephyr Yao <zhihao.yao@njit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Zephyr Yao
2026-07-02 00:17:59 -04:00
committed by Junio C Hamano
parent 94f057755b
commit ffe5c33a44
2 changed files with 47 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
apply.c
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@@ -1362,6 +1362,9 @@ int parse_git_diff_header(struct strbuf *root,
* the default name from the header.
*/
patch->def_name = git_header_name(p_value, line, len);
if (patch->def_name && !*patch->def_name)
FREE_AND_NULL(patch->def_name);
if (patch->def_name && root->len) {
char *s = xstrfmt("%s%s", root->buf, patch->def_name);
free(patch->def_name);
@@ -1632,15 +1635,27 @@ static int find_header(struct apply_state *state,
* or mode change, so we handle that specially
*/
if (!memcmp("diff --git ", line, 11)) {
int git_hdr_len = parse_git_diff_header(&state->root,
state->patch_input_file,
&state->linenr,
state->p_value, line, len,
size, patch);
if (git_hdr_len < 0)
struct patch git_patch = { 0 };
int git_linenr = state->linenr;
int git_hdr_len;
git_patch.inaccurate_eof = patch->inaccurate_eof;
git_patch.recount = patch->recount;
git_hdr_len = parse_git_diff_header(&state->root,
state->patch_input_file,
&git_linenr,
state->p_value, line, len,
size, &git_patch);
if (git_hdr_len < 0) {
release_patch(&git_patch);
return -128;
if (git_hdr_len <= len)
}
if (git_hdr_len <= len) {
release_patch(&git_patch);
continue;
}
*patch = git_patch;
state->linenr = git_linenr;
*hdrsize = git_hdr_len;
return offset;
}