mtd_native: fix overlapping pages write check

cpu/native/mtd/mtd_native.c

@@ -79,14 +79,13 @@ static int _write(mtd_dev_t *dev, const void *buff, uint32_t addr, uint32_t size
 {
     mtd_native_dev_t *_dev = (mtd_native_dev_t*) dev;
     size_t mtd_size = dev->sector_count * dev->pages_per_sector * dev->page_size;
-    size_t sector_size = dev->pages_per_sector * dev->page_size;
 
-    DEBUG("mtd_native: write from page %" PRIu32 " count %" PRIu32 "\n", addr, size);
+    DEBUG("mtd_native: write from 0x%" PRIx32 " count %" PRIu32 "\n", addr, size);
 
     if (addr + size > mtd_size) {
         return -EOVERFLOW;
     }
-    if (((addr % sector_size) + size) > sector_size) {
+    if (((addr % dev->page_size) + size) > dev->page_size) {
         return -EOVERFLOW;
     }
 

tests/unittests/tests-mtd/tests-mtd.c

@@ -69,7 +69,7 @@ static int write(mtd_dev_t *dev, const void *buff, uint32_t addr, uint32_t size)
     if (addr + size > sizeof(dummy_memory)) {
         return -EOVERFLOW;
     }
-    if (size > PAGE_SIZE) {
+    if (((addr % PAGE_SIZE) + size) > PAGE_SIZE) {
         return -EOVERFLOW;
     }
     memcpy(dummy_memory + addr, buff, size);
@@ -212,6 +212,18 @@ static void test_mtd_write_read(void)
     ret = mtd_write(dev, buf, (dev->pages_per_sector * dev->page_size * dev->sector_count)
                     - (sizeof(buf) / 2), sizeof(buf));
     TEST_ASSERT_EQUAL_INT(-EOVERFLOW, ret);
+
+    /* out of bounds write (more than page size) */
+    const size_t page_size = dev->page_size;
+    const uint8_t buf_page[page_size + 1];
+    ret = mtd_write(dev, buf_page, 0, sizeof(buf_page));
+    TEST_ASSERT_EQUAL_INT(-EOVERFLOW, ret);
+
+    /* pages overlap write */
+    ret = mtd_write(dev, buf, dev->page_size - (sizeof(buf) / 2), sizeof(buf));
+    TEST_ASSERT_EQUAL_INT(-EOVERFLOW, ret);
+    ret = mtd_write(dev, buf_page, 1, sizeof(buf_page) - 1);
+    TEST_ASSERT_EQUAL_INT(-EOVERFLOW, ret);
 }
 
 #ifdef MTD_0