range-diff: don't segfault with mode-only changes

In ef283b3699 ("apply: make parse_git_diff_header public", 2019-07-11)
the 'parse_git_diff_header' function was made public and useable by
callers outside of apply.c.

However it was missed that its (then) only caller, 'find_header' did
some error handling, and completing 'struct patch' appropriately.

range-diff then started using this function, and tried to handle this
appropriately itself, but fell short in some cases.  This in turn
would lead to range-diff segfaulting when there are mode-only changes
in a range.

Move the error handling and completing of the struct into the
'parse_git_diff_header' function, so other callers can take advantage
of it.  This fixes the segfault in 'git range-diff'.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 21 deletions

diff --git a/apply.c b/apply.c
index cde9536..5f06a14 100644
--- a/apply.c
+++ b/apply.c
@@ -1361,11 +1361,32 @@ int parse_git_diff_header(struct strbuf *root,
 			if (check_header_line(*linenr, patch))
 				return -1;
 			if (res > 0)
-				return offset;
+				goto done;
 			break;
 		}
 	}
 
+done:
+	if (!patch->old_name && !patch->new_name) {
+		if (!patch->def_name) {
+			error(Q_("git diff header lacks filename information when removing "
+				 "%d leading pathname component (line %d)",
+				 "git diff header lacks filename information when removing "
+				 "%d leading pathname components (line %d)",
+				 parse_hdr_state.p_value),
+			      parse_hdr_state.p_value, *linenr);
+			return -128;
+		}
+		patch->old_name = xstrdup(patch->def_name);
+		patch->new_name = xstrdup(patch->def_name);
+	}
+	if ((!patch->new_name && !patch->is_delete) ||
+	    (!patch->old_name && !patch->is_new)) {
+		error(_("git diff header lacks filename information "
+			"(line %d)"), *linenr);
+		return -128;
+	}
+	patch->is_toplevel_relative = 1;
 	return offset;
 }
 
@@ -1546,26 +1567,6 @@ static int find_header(struct apply_state *state,
 				return -128;
 			if (git_hdr_len <= len)
 				continue;
-			if (!patch->old_name && !patch->new_name) {
-				if (!patch->def_name) {
-					error(Q_("git diff header lacks filename information when removing "
-							"%d leading pathname component (line %d)",
-							"git diff header lacks filename information when removing "
-							"%d leading pathname components (line %d)",
-							state->p_value),
-						     state->p_value, state->linenr);
-					return -128;
-				}
-				patch->old_name = xstrdup(patch->def_name);
-				patch->new_name = xstrdup(patch->def_name);
-			}
-			if ((!patch->new_name && !patch->is_delete) ||
-			    (!patch->old_name && !patch->is_new)) {
-				error(_("git diff header lacks filename information "
-					     "(line %d)"), state->linenr);
-				return -128;
-			}
-			patch->is_toplevel_relative = 1;
 			*hdrsize = git_hdr_len;
 			return offset;
 		}