From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Mon, 9 Nov 2020 15:52:51 +0000 (+0200)
Subject: lib-index: Add explicit wrapping to 8bit variable increments
X-Git-Tag: 2.3.14.rc1~366
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ddf77cf384385b96c115a9b96354816c40803524;p=thirdparty%2Fdovecot%2Fcore.git

lib-index: Add explicit wrapping to 8bit variable increments

Fixes ubsan errors:
runtime error: implicit conversion from type 'int' of value 256 (32-bit, signed) to type 'uint8_t' (aka 'unsigned char') changed the value to 0 (8-bit, unsigned)
---

diff --git a/src/lib-index/mail-cache-lookup.c b/src/lib-index/mail-cache-lookup.c
index a9d20e3136..c0695e4154 100644
--- a/src/lib-index/mail-cache-lookup.c
+++ b/src/lib-index/mail-cache-lookup.c
@@ -330,7 +330,8 @@ static int mail_cache_seq(struct mail_cache_view *view, uint32_t seq)
 	struct mail_cache_iterate_field field;
 	int ret;
 
-	if (++view->cached_exists_value == 0) {
+	view->cached_exists_value = (view->cached_exists_value + 1) % UINT8_MAX;
+	if (view->cached_exists_value == 0) {
 		/* wrapped, we'll have to clear the buffer */
 		buffer_set_used_size(view->cached_exists_buf, 0);
 		view->cached_exists_value++;
diff --git a/src/lib-index/mail-cache-purge.c b/src/lib-index/mail-cache-purge.c
index 907310053a..c61c071295 100644
--- a/src/lib-index/mail-cache-purge.c
+++ b/src/lib-index/mail-cache-purge.c
@@ -293,7 +293,8 @@ mail_cache_copy(struct mail_cache *cache, struct mail_index_transaction *trans,
 		ctx.new_msg = seq >= first_new_seq;
 		buffer_set_used_size(ctx.buffer, 0);
 
-		if (++ctx.field_seen_value == 0) {
+		ctx.field_seen_value = (ctx.field_seen_value + 1) % UINT8_MAX;
+		if (ctx.field_seen_value == 0) {
 			memset(buffer_get_modifiable_data(ctx.field_seen, NULL),
 			       0, buffer_get_size(ctx.field_seen));
 			ctx.field_seen_value++;