Enforce minimum Llama EEPROM size for CRC32 check

matthewlloyd · Jul 11, 2021 · e582d34 · e582d34
1 parent 0548012
commit e582d34
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Showing 2 changed files with 5 additions and 3 deletions.
diff --git a/src/common/llama.cpp b/src/common/llama.cpp
@@ -150,16 +150,16 @@ static uint16_t eeprom_llama_var_offset(uint8_t id) {
 static int eeprom_llama_check_crc32() {
     uint16_t datasize = _eeprom_llama_cache.DATASIZE;
     if (_eeprom_llama_cache.VERSION == 1)
-        datasize = 28;  // before datasize field was added
-    if (datasize < 0 || datasize > EEPROM_LLAMA_DATASIZE) return 0;
+        datasize = EEPROM_LLAMA_MIN_DATASIZE;  // before datasize field was added
+    if (datasize < EEPROM_LLAMA_MIN_DATASIZE || datasize > EEPROM_LLAMA_DATASIZE) return 0;
     uint32_t crc2 = crc32_eeprom((uint32_t *)&_eeprom_llama_cache, (datasize - 4) / 4);
     uint32_t eeprom_crc2 = *((uint32_t*)(((uint8_t*)&_eeprom_llama_cache) + datasize - 4));
     return eeprom_crc2 == crc2 ? 1 : 0;
 }
 
 static void eeprom_llama_update_crc32() {
     uint16_t datasize = _eeprom_llama_cache.DATASIZE;
-    if (datasize < 0 || datasize > EEPROM_LLAMA_DATASIZE) return;
+    if (datasize < EEPROM_LLAMA_MIN_DATASIZE || datasize > EEPROM_LLAMA_DATASIZE) return;
     // calculate crc32
     _eeprom_llama_cache.CRC32 = crc32_eeprom((uint32_t *)&_eeprom_llama_cache, (datasize - 4) / 4);
     // write crc to eeprom

diff --git a/src/common/llama.h b/src/common/llama.h
@@ -80,9 +80,11 @@ typedef struct __attribute__((__packed__)) _eeprom_llama_vars_t {
     uint32_t CRC32;
 } eeprom_llama_vars_t;
 
+#define EEPROM_LLAMA_MIN_DATASIZE (28)
 static_assert(sizeof(eeprom_llama_vars_t) % 4 == 0, "EEPROM_LLAMA__PADDING needs to be adjusted so CRC32 could work.");
 static const constexpr uint32_t EEPROM_LLAMA_VARCOUNT = sizeof(eeprom_llama_map) / sizeof(eeprom_entry_t);
 static const constexpr uint32_t EEPROM_LLAMA_DATASIZE = sizeof(eeprom_llama_vars_t);
+static_assert(EEPROM_LLAMA_DATASIZE >= EEPROM_LLAMA_MIN_DATASIZE, "EEPROM_LLAMA_DATASIZE too small. Only add fields.");
 
 
 // Llama eeprom variable defaults