@matheusbsbs / matheus-bagliano / commits / ffe5c33a44

apply: avoid leaking abandoned git-header state

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>

Zephyr Yao committed Jul 2, 2026 at 00:17 UTC ffe5c33a4423b78e893e340db7387aec8befada7

2 files changed +47 -7

apply.c

+22 -7

@@ -1362,6 +1362,9 @@ int parse_git_diff_header(struct strbuf *root,

1362 * the default name from the header.

1363 */

1364 patch->def_name = git_header_name(p_value, line, len);

1365 + if (patch->def_name && !*patch->def_name)

1366 + FREE_AND_NULL(patch->def_name);

1367 +

1368 if (patch->def_name && root->len) {

1369 char *s = xstrfmt("%s%s", root->buf, patch->def_name);

1370 free(patch->def_name);

@@ -1632,15 +1635,27 @@ static int find_header(struct apply_state *state,

1635 * or mode change, so we handle that specially

1636 */

1637 if (!memcmp("diff --git ", line, 11)) {

1635 - int git_hdr_len = parse_git_diff_header(&state->root,

1636 - state->patch_input_file,

1637 - &state->linenr,

1638 - state->p_value, line, len,

1639 - size, patch);

1640 - if (git_hdr_len < 0)

1638 + struct patch git_patch = { 0 };

1639 + int git_linenr = state->linenr;

1640 + int git_hdr_len;

1641 +

1642 + git_patch.inaccurate_eof = patch->inaccurate_eof;

1643 + git_patch.recount = patch->recount;

1644 + git_hdr_len = parse_git_diff_header(&state->root,

1645 + state->patch_input_file,

1646 + &git_linenr,

1647 + state->p_value, line, len,

1648 + size, &git_patch);

1649 + if (git_hdr_len < 0) {

1650 + release_patch(&git_patch);

1651 return -128;

1642 - if (git_hdr_len <= len)

1652 + }

1653 + if (git_hdr_len <= len) {

1654 + release_patch(&git_patch);

1655 continue;

1656 + }

1657 + *patch = git_patch;

1658 + state->linenr = git_linenr;

1659 *hdrsize = git_hdr_len;

1660 return offset;

1661 }

t/t4100-apply-stat.sh

+25

@@ -113,6 +113,31 @@ test_expect_success 'applying a patch with a missing filename reports the input'

113 test_cmp expect err

114 '

115

116 +test_expect_success 'empty default filename reports the input' '

117 + cat >empty-name.patch <<-\EOF &&

118 + diff --git "a/""b/"

119 +

120 + --- /dev/null

121 + +++ "

122 + @@ -0,0 +1 @@

123 + +

124 + EOF

125 + test_must_fail git apply empty-name.patch 2>err &&

126 + test_grep "git diff header lacks filename information" err

127 +'

128 +

129 +test_expect_success 'abandoned git header does not reuse names' '

130 + cat >abandoned-git-header.patch <<-\EOF &&

131 + diff --git a/foo b/foo

132 +

133 + --- /dev/null

134 + +++ b/foo

135 + @@ -0,0 +1 @@

136 + +x

137 + EOF

138 + git apply --check abandoned-git-header.patch

139 +'

140 +

141 test_expect_success 'applying a patch with an invalid mode reports the input' '

142 cat >mode.patch <<-\EOF &&

143 diff --git a/f b/f