replace snprintf with odb_pack_name()

In several places we write the name of the pack filename
into a fixed-size buffer using snprintf(), but do not check
the return value.  As a result, a very long object directory
could cause us to quietly truncate the pack filename
(potentially leading to a corrupted repository, as a newly
written packfile could be missing its .pack extension).

We can use odb_pack_name() to do this with a strbuf (and
shorten the code, as well).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -1386,7 +1386,7 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 		  unsigned char *sha1)
 {
 	const char *report = "pack";
-	char name[PATH_MAX];
+	struct strbuf name = STRBUF_INIT;
 	int err;
 
 	if (!from_stdin) {
@@ -1402,14 +1402,13 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 		int keep_fd, keep_msg_len = strlen(keep_msg);
 
 		if (!keep_name)
-			snprintf(name, sizeof(name), "%s/pack/pack-%s.keep",
-				 get_object_directory(), sha1_to_hex(sha1));
+			odb_pack_name(&name, sha1, "keep");
 
-		keep_fd = odb_pack_keep(keep_name ? keep_name : name);
+		keep_fd = odb_pack_keep(keep_name ? keep_name : name.buf);
 		if (keep_fd < 0) {
 			if (errno != EEXIST)
 				die_errno(_("cannot write keep file '%s'"),
-					  keep_name ? keep_name : name);
+					  keep_name ? keep_name : name.buf);
 		} else {
 			if (keep_msg_len > 0) {
 				write_or_die(keep_fd, keep_msg, keep_msg_len);
@@ -1417,28 +1416,22 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 			}
 			if (close(keep_fd) != 0)
 				die_errno(_("cannot close written keep file '%s'"),
-					  keep_name ? keep_name : name);
+					  keep_name ? keep_name : name.buf);
 			report = "keep";
 		}
 	}
 
 	if (final_pack_name != curr_pack_name) {
-		if (!final_pack_name) {
-			snprintf(name, sizeof(name), "%s/pack/pack-%s.pack",
-				 get_object_directory(), sha1_to_hex(sha1));
-			final_pack_name = name;
-		}
+		if (!final_pack_name)
+			final_pack_name = odb_pack_name(&name, sha1, "pack");
 		if (finalize_object_file(curr_pack_name, final_pack_name))
 			die(_("cannot store pack file"));
 	} else if (from_stdin)
 		chmod(final_pack_name, 0444);
 
 	if (final_index_name != curr_index_name) {
-		if (!final_index_name) {
-			snprintf(name, sizeof(name), "%s/pack/pack-%s.idx",
-				 get_object_directory(), sha1_to_hex(sha1));
-			final_index_name = name;
-		}
+		if (!final_index_name)
+			final_index_name = odb_pack_name(&name, sha1, "idx");
 		if (finalize_object_file(curr_index_name, final_index_name))
 			die(_("cannot store index file"));
 	} else
@@ -1464,6 +1457,8 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 			input_offset += err;
 		}
 	}
+
+	strbuf_release(&name);
 }
 
 static int git_index_pack_config(const char *k, const char *v, void *cb)

fast-import.c

@@ -940,43 +940,40 @@ static const char *create_index(void)
 
 static char *keep_pack(const char *curr_index_name)
 {
-	static char name[PATH_MAX];
 	static const char *keep_msg = "fast-import";
+	struct strbuf name = STRBUF_INIT;
 	int keep_fd;
 
-	snprintf(name, sizeof(name), "%s/pack/pack-%s.keep",
-		 get_object_directory(), sha1_to_hex(pack_data->sha1));
-	keep_fd = odb_pack_keep(name);
+	odb_pack_name(&name, pack_data->sha1, "keep");
+	keep_fd = odb_pack_keep(name.buf);
 	if (keep_fd < 0)
 		die_errno("cannot create keep file");
 	write_or_die(keep_fd, keep_msg, strlen(keep_msg));
 	if (close(keep_fd))
 		die_errno("failed to write keep file");
 
-	snprintf(name, sizeof(name), "%s/pack/pack-%s.pack",
-		 get_object_directory(), sha1_to_hex(pack_data->sha1));
-	if (finalize_object_file(pack_data->pack_name, name))
+	odb_pack_name(&name, pack_data->sha1, "pack");
+	if (finalize_object_file(pack_data->pack_name, name.buf))
 		die("cannot store pack file");
 
-	snprintf(name, sizeof(name), "%s/pack/pack-%s.idx",
-		 get_object_directory(), sha1_to_hex(pack_data->sha1));
-	if (finalize_object_file(curr_index_name, name))
+	odb_pack_name(&name, pack_data->sha1, "idx");
+	if (finalize_object_file(curr_index_name, name.buf))
 		die("cannot store index file");
 	free((void *)curr_index_name);
-	return name;
+	return strbuf_detach(&name, NULL);
 }
 
 static void unkeep_all_packs(void)
 {
-	static char name[PATH_MAX];
+	struct strbuf name = STRBUF_INIT;
 	int k;
 
 	for (k = 0; k < pack_id; k++) {
 		struct packed_git *p = all_packs[k];
-		snprintf(name, sizeof(name), "%s/pack/pack-%s.keep",
-			 get_object_directory(), sha1_to_hex(p->sha1));
-		unlink_or_warn(name);
+		odb_pack_name(&name, p->sha1, "keep");
+		unlink_or_warn(name.buf);
 	}
+	strbuf_release(&name);
 }
 
 static int loosen_small_pack(const struct packed_git *p)
@@ -1035,6 +1032,7 @@ static void end_packfile(void)
 			die("core git rejected index %s", idx_name);
 		all_packs[pack_id] = new_p;
 		install_packed_git(new_p);
+		free(idx_name);
 
 		/* Print the boundary */
 		if (pack_edges) {