Merge pull request wolfSSL#54 from danielinux/fifo_no_space_off_by_one

Fix off-by-one comparison in space calculation

Author: gasbytes

src/test/unit/unit.c

@@ -14220,6 +14220,45 @@ START_TEST(test_fifo_push_wrap_multiple) {
 }
 END_TEST
 
+START_TEST(test_fifo_push_wrap_tail_equals_needed)
+{
+    struct fifo f;
+    uint8_t buffer[64];
+    uint8_t payload[8] = {0xAA, 0xBB, 0xCC, 0xDD, 0x11, 0x22, 0x33, 0x44};
+    uint32_t needed = (uint32_t)(sizeof(struct pkt_desc) + sizeof(payload));
+    struct pkt_desc *desc;
+
+    fifo_init(&f, buffer, sizeof(buffer));
+    f.head = 60;
+    f.tail = needed;
+    f.h_wrap = 0;
+
+    ck_assert_int_eq(fifo_push(&f, payload, sizeof(payload)), 0);
+    ck_assert_uint_eq(f.h_wrap, 60U);
+    ck_assert_uint_eq(f.head, needed);
+
+    desc = (struct pkt_desc *)buffer;
+    ck_assert_uint_eq(desc->pos, 0U);
+    ck_assert_uint_eq(desc->len, sizeof(payload));
+}
+END_TEST
+
+START_TEST(test_fifo_can_push_len_wrap_tail_equals_needed)
+{
+    struct fifo f;
+    uint8_t buffer[64];
+    uint32_t len = 8U;
+    uint32_t needed = (uint32_t)(sizeof(struct pkt_desc) + len);
+
+    fifo_init(&f, buffer, sizeof(buffer));
+    f.head = 60;
+    f.tail = needed;
+    f.h_wrap = 0;
+
+    ck_assert_int_eq(fifo_can_push_len(&f, len), 1);
+}
+END_TEST
+
 START_TEST(test_fifo_space_wrap_sets_hwrap)
 {
     struct fifo f;
@@ -16991,6 +17030,8 @@ Suite *wolf_suite(void)
     tcase_add_test(tc_core, test_fifo_can_push_len_head_at_wrap_boundary);
     tcase_add_test(tc_core, test_fifo_push_wrap);
     tcase_add_test(tc_core, test_fifo_push_wrap_multiple);
+    tcase_add_test(tc_core, test_fifo_push_wrap_tail_equals_needed);
+    tcase_add_test(tc_core, test_fifo_can_push_len_wrap_tail_equals_needed);
     tcase_add_test(tc_core, test_fifo_space_wrap_sets_hwrap);
     tcase_add_test(tc_core, test_fifo_space_wrap_returns_zero);
     tcase_add_test(tc_core, test_fifo_peek_wrap_to_start);

src/wolfip.c

@@ -338,7 +338,7 @@ static int fifo_push(struct fifo *f, void *data, uint32_t len)
     if (h_wrap == 0 && head >= tail) {
         uint32_t end_space = f->size - head;
         if (end_space < needed) {
-            if (tail <= needed)
+            if (tail < needed)
                 return -1;
             h_wrap = head;
             head = 0;
@@ -410,7 +410,7 @@ static int fifo_can_push_len(const struct fifo *fin, uint32_t len)
     if (h_wrap == 0 && head >= tail) {
         uint32_t end_space = fin->size - head;
         if (end_space < needed) {
-            if (tail <= needed)
+            if (tail < needed)
                 return 0;
             h_wrap = head;
             head = 0;