From a9dea12eb8d60bc531c69887edaef535635b920d Mon Sep 17 00:00:00 2001
From: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Date: Thu, 6 May 2021 09:23:22 +0200
Subject: [PATCH] cpu/esp_common: add overflow detection to calloc

If esp_idf_heap is not used, implement calloc through a custom wrapper
function on top of malloc to add overflow detection, which is not
present in the newlib forks with xtensa support yet.
---
 cpu/esp32/vendor/esp-idf/heap/heap_trace.c |  9 ++++++---
 cpu/esp_common/Makefile.include            |  6 ++++++
 cpu/esp_common/syscalls.c                  | 19 +++++++++++++++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/cpu/esp32/vendor/esp-idf/heap/heap_trace.c b/cpu/esp32/vendor/esp-idf/heap/heap_trace.c
index de703f5f4c..577a09da3a 100644
--- a/cpu/esp32/vendor/esp-idf/heap/heap_trace.c
+++ b/cpu/esp32/vendor/esp-idf/heap/heap_trace.c
@@ -407,10 +407,13 @@ IRAM_ATTR void *__wrap_realloc(void *p, size_t size)
 
 IRAM_ATTR void *__wrap_calloc(size_t nmemb, size_t size)
 {
-    size = size * nmemb;
-    void *result = trace_malloc(size, 0, TRACE_MALLOC_DEFAULT);
+    size_t total_size;
+    if (__builtin_mul_overflow(nmemb, size, &total_size)) {
+        return NULL;
+    }
+    void *result = trace_malloc(total_size, 0, TRACE_MALLOC_DEFAULT);
     if (result != NULL) {
-        memset(result, 0, size);
+        memset(result, 0, total_size);
     }
     return result;
 }
diff --git a/cpu/esp_common/Makefile.include b/cpu/esp_common/Makefile.include
index 63109cc4ec..684afff317 100644
--- a/cpu/esp_common/Makefile.include
+++ b/cpu/esp_common/Makefile.include
@@ -85,6 +85,12 @@ LINKFLAGS += -L$(ESP_SDK_DIR)/components/$(CPU)
 LINKFLAGS += -L$(ESP_SDK_DIR)/components/$(CPU)/lib
 LINKFLAGS += -nostdlib -Wl,-gc-sections -Wl,-static
 
+ifeq (,$(filter esp_idf_heap,$(USEMODULE)))
+  # use the wrapper functions for calloc to add correct overflow detection missing
+  # in the newlib's version.
+  LINKFLAGS += -Wl,-wrap=calloc
+endif
+
 # LINKFLAGS += -Wl,--verbose
 # LINKFLAGS += -Wl,--print-gc-sections
 
diff --git a/cpu/esp_common/syscalls.c b/cpu/esp_common/syscalls.c
index 9bc337dc61..b1c5f9fe76 100644
--- a/cpu/esp_common/syscalls.c
+++ b/cpu/esp_common/syscalls.c
@@ -289,6 +289,25 @@ void* IRAM_ATTR __wrap__calloc_r(struct _reent *r, size_t count, size_t size)
 
 #else /* MODULE_ESP_IDF_HEAP */
 
+void *__wrap_calloc(size_t nmemb, size_t size)
+{
+    /* The xtensa support has not yet upstreamed to newlib. Hence, the fixed
+     * calloc implementation of newlib >= 4.0.0 is not available to the ESP
+     * platform. We fix this by implementing calloc on top of malloc ourselves */
+    size_t total_size;
+    if (__builtin_mul_overflow(nmemb, size, &total_size)) {
+        return NULL;
+    }
+
+    void *res = malloc(total_size);
+
+    if (res) {
+        memset(res, 0, total_size);
+    }
+
+    return res;
+}
+
 /* for compatibility with ESP-IDF heap functions */
 
 void* _heap_caps_malloc(size_t size, uint32_t caps, const char *file, size_t line)