use st_add and st_mult for allocation size computation

If our size computation overflows size_t, we may allocate a
much smaller buffer than we expected and overflow it. It's
probably impossible to trigger an overflow in most of these
sites in practice, but it is easy enough convert their
additions and multiplications into overflow-checking
variants. This may be fixing real bugs, and it makes
auditing the code easier.

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

7 files changed, 9 insertions, 9 deletions

diff --git a/builtin/apply.c b/builtin/apply.c
index deb1364fa8..0db6d14cc2 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -2632,7 +2632,7 @@ static void update_image(struct image *img,
 	insert_count = postimage->len;
 
 	/* Adjust the contents */
-	result = xmalloc(img->len + insert_count - remove_count + 1);
+	result = xmalloc(st_add3(st_sub(img->len, remove_count), insert_count, 1));
 	memcpy(result, img->buf, applied_at);
 	memcpy(result + applied_at, postimage->buf, postimage->len);
 	memcpy(result + applied_at + postimage->len,
diff --git a/builtin/clean.c b/builtin/clean.c
index 1f02c8294c..fb1824ce95 100644
--- a/builtin/clean.c
+++ b/builtin/clean.c
@@ -615,7 +615,7 @@ static int *list_and_choose(struct menu_opts *opts, struct menu_stuff *stuff)
 				nr += chosen[i];
 		}
 
-		result = xcalloc(nr + 1, sizeof(int));
+		result = xcalloc(st_add(nr, 1), sizeof(int));
 		for (i = 0; i < stuff->nr && j < nr; i++) {
 			if (chosen[i])
 				result[j++] = i;
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 17f40e10f6..683f08ec91 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1107,7 +1107,7 @@ static int fetch_one(struct remote *remote, int argc, const char **argv)
 	if (argc > 0) {
 		int j = 0;
 		int i;
-		refs = xcalloc(argc + 1, sizeof(const char *));
+		refs = xcalloc(st_add(argc, 1), sizeof(const char *));
 		for (i = 0; i < argc; i++) {
 			if (!strcmp(argv[i], "tag")) {
 				i++;
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index a60bcfac06..193908a619 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -1744,9 +1744,9 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 
 	curr_pack = open_pack_file(pack_name);
 	parse_pack_header();
-	objects = xcalloc(nr_objects + 1, sizeof(struct object_entry));
+	objects = xcalloc(st_add(nr_objects, 1), sizeof(struct object_entry));
 	if (show_stat)
-		obj_stat = xcalloc(nr_objects + 1, sizeof(struct object_stat));
+		obj_stat = xcalloc(st_add(nr_objects, 1), sizeof(struct object_stat));
 	ofs_deltas = xcalloc(nr_objects, sizeof(struct ofs_delta_entry));
 	parse_pack_objects(pack_sha1);
 	resolve_deltas();
diff --git a/builtin/merge.c b/builtin/merge.c
index b98a3489bf..101ffeff4c 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -939,7 +939,7 @@ static int setup_with_upstream(const char ***argv)
 	if (!branch->merge_nr)
 		die(_("No default upstream defined for the current branch."));
 
-	args = xcalloc(branch->merge_nr + 1, sizeof(char *));
+	args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 	for (i = 0; i < branch->merge_nr; i++) {
 		if (!branch->merge[i]->dst)
 			die(_("No remote-tracking branch for %s from %s"),
diff --git a/builtin/mv.c b/builtin/mv.c
index 9a9813a0ec..aeae855e2b 100644
--- a/builtin/mv.c
+++ b/builtin/mv.c
@@ -48,9 +48,9 @@ static const char **internal_copy_pathspec(const char *prefix,
 
 static const char *add_slash(const char *path)
 {
-	int len = strlen(path);
+	size_t len = strlen(path);
 	if (path[len - 1] != '/') {
-		char *with_slash = xmalloc(len + 2);
+		char *with_slash = xmalloc(st_add(len, 2));
 		memcpy(with_slash, path, len);
 		with_slash[len++] = '/';
 		with_slash[len] = 0;
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 3dc3868c86..c8e32b297c 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1372,7 +1372,7 @@ static struct command **queue_command(struct command **tail,
 
 	refname = line + 82;
 	reflen = linelen - 82;
-	cmd = xcalloc(1, sizeof(struct command) + reflen + 1);
+	cmd = xcalloc(1, st_add3(sizeof(struct command), reflen, 1));
 	hashcpy(cmd->old_sha1, old_sha1);
 	hashcpy(cmd->new_sha1, new_sha1);
 	memcpy(cmd->ref_name, refname, reflen);