diff --git a/_imaging.c b/_imaging.c
index 68102b611..c6adcde15 100644
--- a/_imaging.c
+++ b/_imaging.c
@@ -362,9 +362,20 @@ getbands(const char* mode)
 #define TYPE_DOUBLE (0x400|sizeof(double))
 
 static void*
-getlist(PyObject* arg, int* length, const char* wrong_length, int type)
+getlist(PyObject* arg, Py_ssize_t* length, const char* wrong_length, int type)
 {
-    int i, n, itemp;
+    /* - allocates and returns a c array of the items in the 
+          python sequence arg.
+       - the size of the returned array is in length
+       - all of the arg items must be numeric items of the type 
+          specified in type
+       - sequence length is checked against the length parameter IF
+          an error parameter is passed in wrong_length
+       - caller is responsible for freeing the memory    
+    */
+
+    Py_ssize_t i, n; 
+    int itemp;
     double dtemp;
     void* list;
     PyObject* seq;
@@ -376,12 +387,14 @@ getlist(PyObject* arg, int* length, const char* wrong_length, int type)
     }
 
     n = PyObject_Length(arg);
-    if (length && wrong_length && n != *length) {
+    if (length && wrong_length && n !=  *length) {
         PyErr_SetString(PyExc_ValueError, wrong_length);
         return NULL;
     }
 
-    list = malloc(n * (type & 0xff));
+    /* malloc check ok, type & ff is just a sizeof(something)
+       calloc checks for overflow */
+    list = calloc(n, type & 0xff);
     if (!list)
         return PyErr_NoMemory();
 
@@ -845,7 +858,7 @@ static PyObject*
 _filter(ImagingObject* self, PyObject* args)
 {
     PyObject* imOut;
-    int kernelsize;
+    Py_ssize_t kernelsize;
     FLOAT32* kerneldata;
 
     int xsize, ysize;
@@ -859,7 +872,7 @@ _filter(ImagingObject* self, PyObject* args)
     kerneldata = getlist(kernel, &kernelsize, NULL, TYPE_FLOAT32);
     if (!kerneldata)
         return NULL;
-    if (kernelsize != xsize * ysize) {
+    if (kernelsize != (Py_ssize_t) xsize * (Py_ssize_t) ysize) {
         free(kerneldata);
         return ImagingError_ValueError("bad kernel size");
     }
@@ -1148,8 +1161,8 @@ _point(ImagingObject* self, PyObject* args)
 {
     static const char* wrong_number = "wrong number of lut entries";
 
-    int n, i;
-    int bands;
+    Py_ssize_t n;
+    int i, bands;
     Imaging im;
 
     PyObject* list;
@@ -1664,7 +1677,7 @@ _transform2(ImagingObject* self, PyObject* args)
 
     Imaging imIn;
     Imaging imOut;
-    int n;
+    Py_ssize_t n;
     double *a;
 
     ImagingObject* imagep;
@@ -1920,6 +1933,7 @@ _getprojection(ImagingObject* self, PyObject* args)
     unsigned char* yprofile;
     PyObject* result;
 
+    /* malloc check ok */
     xprofile = malloc(self->image->xsize);
     yprofile = malloc(self->image->ysize);
 
@@ -2731,7 +2745,7 @@ _draw_polygon(ImagingDrawObject* self, PyObject* args)
     }
 
     /* Copy list of vertices to array */
-    ixy = (int*) malloc(n * 2 * sizeof(int));
+    ixy = (int*) calloc(n, 2 * sizeof(int));
 
     for (i = 0; i < n; i++) {
         ixy[i+i] = (int) xy[i+i];
diff --git a/decode.c b/decode.c
index 29c0f9a1b..0c66243cd 100644
--- a/decode.c
+++ b/decode.c
@@ -188,8 +188,13 @@ _setimage(ImagingDecoderObject* decoder, PyObject* args)
 
     /* Allocate memory buffer (if bits field is set) */
     if (state->bits > 0) {
-        if (!state->bytes)
+        if (!state->bytes) {
+            if (state->xsize > ((SIZE_MAX / state->bits)-7)){
+                return PyErr_NoMemory();
+            }
             state->bytes = (state->bits * state->xsize+7)/8;
+        }
+        /* malloc check ok, oveflow checked above */
         state->buffer = (UINT8*) malloc(state->bytes);
         if (!state->buffer)
             return PyErr_NoMemory();
diff --git a/encode.c b/encode.c
index 84e5b96b1..d821a54df 100644
--- a/encode.c
+++ b/encode.c
@@ -159,6 +159,7 @@ _encode_to_file(ImagingEncoderObject* encoder, PyObject* args)
         return NULL;
 
     /* Allocate an encoder buffer */
+    /* malloc check ok, either constant int, or checked by PyArg_ParseTuple */
     buf = (UINT8*) malloc(bufsize);
     if (!buf)
         return PyErr_NoMemory();
@@ -233,7 +234,11 @@ _setimage(ImagingEncoderObject* encoder, PyObject* args)
 
     /* Allocate memory buffer (if bits field is set) */
     if (state->bits > 0) {
+        if (state->xsize > ((SIZE_MAX / state->bits)-7)) {
+            return PyErr_NoMemory();
+        }
         state->bytes = (state->bits * state->xsize+7)/8;
+        /* malloc check ok, overflow checked above */
         state->buffer = (UINT8*) malloc(state->bytes);
         if (!state->buffer)
             return PyErr_NoMemory();
@@ -482,6 +487,7 @@ PyImaging_ZipEncoderNew(PyObject* self, PyObject* args)
        free this memory later, so this function (and several others here)
        leaks. */
     if (dictionary && dictionary_size > 0) {
+        /* malloc check ok, size comes from PyArg_ParseTuple */
         char* p = malloc(dictionary_size);
         if (!p)
             return PyErr_NoMemory();
@@ -559,6 +565,7 @@ static unsigned int* get_qtables_arrays(PyObject* qtables, int* qtablesLen) {
         Py_DECREF(tables);
         return NULL;
     }
+    /* malloc check ok, num_tables <4, DCTSIZE2 == 64 from jpeglib.h */
     qarrays = (unsigned int*) malloc(num_tables * DCTSIZE2 * sizeof(unsigned int));
     if (!qarrays) {
         Py_DECREF(tables);
@@ -634,6 +641,7 @@ PyImaging_JpegEncoderNew(PyObject* self, PyObject* args)
     qarrays = get_qtables_arrays(qtables, &qtablesLen);
 
     if (extra && extra_size > 0) {
+        /* malloc check ok, length is from python parsearg */
         char* p = malloc(extra_size); // Freed in JpegEncode, Case 5
         if (!p)
             return PyErr_NoMemory();
@@ -643,6 +651,7 @@ PyImaging_JpegEncoderNew(PyObject* self, PyObject* args)
         extra = NULL;
 
     if (rawExif && rawExifLen > 0) {
+        /* malloc check ok, length is from python parsearg */
         char* pp = malloc(rawExifLen); // Freed in JpegEncode, Case 5
         if (!pp)
             return PyErr_NoMemory();
@@ -757,15 +766,16 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
                                             (ttag_t) PyInt_AsLong(key),
                                             PyBytes_AsString(value));
         } else if (PyTuple_Check(value)) {
-            int len,i;
+            Py_ssize_t len,i;
             float *floatav;
             int *intav;
             TRACE(("Setting from Tuple: %d \n", (int)PyInt_AsLong(key)));
-            len = (int)PyTuple_Size(value);
+            len = PyTuple_Size(value);
             if (len) {
                 if (PyInt_Check(PyTuple_GetItem(value,0))) {
-                    TRACE((" %d elements, setting as ints \n", len));
-                    intav = malloc(sizeof(int)*len);
+                    TRACE((" %d elements, setting as ints \n", (int)len));
+                    /* malloc check ok, calloc checks for overflow */
+                    intav = calloc(len, sizeof(int));
                     if (intav) {
                         for (i=0;i<len;i++) {
                             intav[i] = (int)PyInt_AsLong(PyTuple_GetItem(value,i));
@@ -776,8 +786,9 @@ PyImaging_LibTiffEncoderNew(PyObject* self, PyObject* args)
                         free(intav);
                     }
                 } else if (PyFloat_Check(PyTuple_GetItem(value,0))) {
-                    TRACE((" %d elements, setting as floats \n", len));
-                    floatav = malloc(sizeof(float)*len);
+                    TRACE((" %d elements, setting as floats \n", (int)len));
+                    /* malloc check ok, calloc checks for overflow */
+                    floatav = calloc(len, sizeof(float));
                     if (floatav) {
                         for (i=0;i<len;i++) {
                             floatav[i] = (float)PyFloat_AsDouble(PyTuple_GetItem(value,i));
diff --git a/libImaging/Dib.c b/libImaging/Dib.c
index 9e2a910be..504290231 100644
--- a/libImaging/Dib.c
+++ b/libImaging/Dib.c
@@ -70,9 +70,11 @@ ImagingNewDIB(const char *mode, int xsize, int ysize)
         return (ImagingDIB) ImagingError_ModeError();
 
     /* Create DIB context and info header */
+    /* malloc check ok, small constant allocation */
     dib = (ImagingDIB) malloc(sizeof(*dib));
     if (!dib)
         return (ImagingDIB) ImagingError_MemoryError();
+    /* malloc check ok, small constant allocation */
     dib->info = (BITMAPINFO*) malloc(sizeof(BITMAPINFOHEADER) +
                                      256 * sizeof(RGBQUAD));
     if (!dib->info) {
diff --git a/libImaging/Draw.c b/libImaging/Draw.c
index 423f1bea2..9bc5800b9 100644
--- a/libImaging/Draw.c
+++ b/libImaging/Draw.c
@@ -434,7 +434,8 @@ polygon_generic(Imaging im, int n, Edge *e, int ink, int eofill,
     }
 
     /* Initialize the edge table and find polygon boundaries */
-    edge_table = malloc(sizeof(Edge*) * n);
+    /* malloc check ok, using calloc */
+    edge_table = calloc(n, sizeof(Edge*));
     if (!edge_table) {
         return -1;
     }
@@ -462,7 +463,8 @@ polygon_generic(Imaging im, int n, Edge *e, int ink, int eofill,
     }
 
     /* Process the edge table with a scan line searching for intersections */
-    xx = malloc(sizeof(float) * edge_count * 2);
+    /* malloc check ok, using calloc */ 
+    xx = calloc(edge_count * 2, sizeof(float));
     if (!xx) {
         free(edge_table);
         return -1;
@@ -700,7 +702,8 @@ ImagingDrawPolygon(Imaging im, int count, int* xy, const void* ink_,
     if (fill) {
 
         /* Build edge list */
-        Edge* e = malloc(count * sizeof(Edge));
+        /* malloc check ok, using calloc */
+        Edge* e = calloc(count, sizeof(Edge));
         if (!e) {
             (void) ImagingError_MemoryError();
             return -1;
@@ -772,7 +775,8 @@ ellipse(Imaging im, int x0, int y0, int x1, int y1,
     if (mode != ARC && fill) {
 
         /* Build edge list */
-        Edge* e = malloc((end - start + 3) * sizeof(Edge));
+        /* malloc check UNDONE, FLOAT? */
+        Edge* e = calloc((end - start + 3), sizeof(Edge));
         if (!e) {
             ImagingError_MemoryError();
             return -1;
@@ -930,8 +934,11 @@ allocate(ImagingOutline outline, int extra)
         /* expand outline buffer */
         outline->size += extra + 25;
         if (!outline->edges)
-            e = malloc(outline->size * sizeof(Edge));
+            /* malloc check ok, uses calloc for overflow */
+            e = calloc(outline->size, sizeof(Edge));
         else
+            /* malloc check UNDONE, overflow, realloc to larger, 
+               if it fails, it will leak memory */
             e = realloc(outline->edges, outline->size * sizeof(Edge));
         if (!e)
             return NULL;
diff --git a/libImaging/Geometry.c b/libImaging/Geometry.c
index 97cbcf2ed..df4f79fd7 100644
--- a/libImaging/Geometry.c
+++ b/libImaging/Geometry.c
@@ -712,8 +712,9 @@ ImagingScaleAffine(Imaging imOut, Imaging imIn,
         x1 = imOut->xsize;
     if (y1 > imOut->ysize)
         y1 = imOut->ysize;
-
-    xintab = (int*) malloc(imOut->xsize * sizeof(int));
+    
+    /* malloc check ok, uses calloc for overflow */
+    xintab = (int*) calloc(imOut->xsize, sizeof(int));
     if (!xintab) {
         ImagingDelete(imOut);
         return (Imaging) ImagingError_MemoryError();
diff --git a/libImaging/GifEncode.c b/libImaging/GifEncode.c
index 4ada55496..f211814ed 100644
--- a/libImaging/GifEncode.c
+++ b/libImaging/GifEncode.c
@@ -61,6 +61,7 @@ emit(GIFENCODERSTATE *context, int byte)
             block = context->free;
             context->free = NULL;
         } else {
+            /* malloc check ok, small constant allocation */
             block = malloc(sizeof(GIFENCODERBLOCK));
             if (!block)
                 return 0;
diff --git a/libImaging/Incremental.c b/libImaging/Incremental.c
index f34765423..68776992a 100644
--- a/libImaging/Incremental.c
+++ b/libImaging/Incremental.c
@@ -168,6 +168,7 @@ ImagingIncrementalCodecCreate(ImagingIncrementalCodecEntry codec_entry,
                               int seekable,
                               int fd)
 {
+    /* malloc check ok, small constant allocation */  
   ImagingIncrementalCodec codec = (ImagingIncrementalCodec)malloc(sizeof(struct ImagingIncrementalCodecStruct));
 
   codec->entry = codec_entry;
diff --git a/libImaging/Palette.c b/libImaging/Palette.c
index 93de49f20..31c2c0245 100644
--- a/libImaging/Palette.c
+++ b/libImaging/Palette.c
@@ -103,7 +103,7 @@ ImagingPaletteDuplicate(ImagingPalette palette)
 
     if (!palette)
         return NULL;
-
+    /* malloc check ok, small constant allocation */
     new_palette = malloc(sizeof(struct ImagingPaletteInstance));
     if (!new_palette)
         return (ImagingPalette) ImagingError_MemoryError();
@@ -288,6 +288,7 @@ ImagingPaletteCachePrepare(ImagingPalette palette)
         /* The cache is 512k.  It might be a good idea to break it
            up into a pointer array (e.g. an 8-bit image?) */
 
+        /* malloc check ok, small constant allocation */
         palette->cache = (INT16*) malloc(entries * sizeof(INT16));
         if (!palette->cache) {
             (void) ImagingError_MemoryError();
diff --git a/libImaging/Quant.c b/libImaging/Quant.c
index 6c122eee2..e16646b96 100644
--- a/libImaging/Quant.c
+++ b/libImaging/Quant.c
@@ -150,6 +150,7 @@ create_pixel_hash(Pixel *pixelData,uint32_t nPixels)
    uint32_t timer,timer2,timer3;
 #endif
 
+   /* malloc check ok, small constant allocation */
    d=malloc(sizeof(PixelHashData));
    if (!d) return NULL;
    hash=hashtable_new(pixel_hash,pixel_cmp);
@@ -234,6 +235,7 @@ hash_to_list(const HashTable *h, const Pixel pixel, const uint32_t count, void *
 
    PIXEL_SCALE(&pixel,&q,d->scale);
 
+   /* malloc check ok, small constant allocation */
    p=malloc(sizeof(PixelList));
    if (!p) return;
 
@@ -557,6 +559,7 @@ split(BoxNode *node)
       exit(1);
    }
 #endif
+   /* malloc check ok, small constant allocation */
    left=malloc(sizeof(BoxNode));
    right=malloc(sizeof(BoxNode));
    if (!left||!right) {
@@ -613,6 +616,7 @@ median_cut(PixelList *hl[3],
    BoxNode *thisNode;
 
    h=ImagingQuantHeapNew(box_heap_cmp);
+   /* malloc check ok, small constant allocation */
    root=malloc(sizeof(BoxNode));
    if (!root) { ImagingQuantHeapFree(h); return NULL; }
    for(i=0;i<3;i++) {
@@ -954,15 +958,16 @@ compute_palette_from_median_cut(
    uint32_t *count;
 
    *palette=NULL;
-   if (!(count=malloc(sizeof(uint32_t)*nPaletteEntries))) {
+   /* malloc check ok, using calloc */
+   if (!(count=calloc(nPaletteEntries, sizeof(uint32_t)))) {
       return 0;
    }
-   memset(count,0,sizeof(uint32_t)*nPaletteEntries);
    for(i=0;i<3;i++) {
       avg[i]=NULL;
    }
    for(i=0;i<3;i++) {
-      if (!(avg[i]=malloc(sizeof(uint32_t)*nPaletteEntries))) {
+      /* malloc check ok, using calloc */     
+      if (!(avg[i]=calloc(nPaletteEntries, sizeof(uint32_t)))) {
          for(i=0;i<3;i++) {
             if (avg[i]) free (avg[i]);
          }
@@ -970,9 +975,6 @@ compute_palette_from_median_cut(
          return 0;
       }
    }
-   for(i=0;i<3;i++) {
-      memset(avg[i],0,sizeof(uint32_t)*nPaletteEntries);
-   }
    for (i=0;i<nPixels;i++) {
 #ifdef TEST_SPLIT_INTEGRITY
       if (!(i%100)) { printf ("%05d\r",i); fflush(stdout); }
@@ -1004,7 +1006,8 @@ compute_palette_from_median_cut(
       avg[2][paletteEntry]+=pixelData[i].c.b;
       count[paletteEntry]++;
    }
-   p=malloc(sizeof(Pixel)*nPaletteEntries);
+   /* malloc check ok, using calloc */
+   p=calloc(nPaletteEntries, sizeof(Pixel));
    if (!p) {
       for(i=0;i<3;i++) free (avg[i]);
       free(count);
@@ -1089,22 +1092,30 @@ k_means(Pixel *pixelData,
    uint32_t **avgDistSortKey;
    int changes;
    int built=0;
-
-   if (!(count=malloc(sizeof(uint32_t)*nPaletteEntries))) {
+   /* malloc check ok, using calloc */
+   if (!(count=calloc(nPaletteEntries, sizeof(uint32_t)))) {
       return 0;
    }
    for(i=0;i<3;i++) {
       avg[i]=NULL;
    }
    for(i=0;i<3;i++) {
-      if (!(avg[i]=malloc(sizeof(uint32_t)*nPaletteEntries))) {
+      /* malloc check ok, using calloc */
+      if (!(avg[i]=calloc(nPaletteEntries, sizeof(uint32_t)))) {
          goto error_1;
       }
    }
-   avgDist=malloc(sizeof(uint32_t)*nPaletteEntries*nPaletteEntries);
+   
+   /* this is enough of a check, since the multiplication n*size is done above */
+   if (nPaletteEntries > SIZE_MAX / (nPaletteEntries * sizeof(uint32_t))) {
+       goto error_1;
+   }
+   /* malloc check ok, using calloc, checking n*n above */
+   avgDist=calloc(nPaletteEntries*nPaletteEntries, sizeof(uint32_t));
    if (!avgDist) { goto error_1; }
 
-   avgDistSortKey=malloc(sizeof(uint32_t *)*nPaletteEntries*nPaletteEntries);
+   /* malloc check ok, using calloc, checking n*n above */
+   avgDistSortKey=calloc(nPaletteEntries*nPaletteEntries, sizeof(uint32_t *));
    if (!avgDistSortKey) { goto error_2; }
 
 #ifndef NO_OUTPUT
@@ -1251,13 +1262,20 @@ quantize(Pixel *pixelData,
    free_box_tree(root);
    root=NULL;
 
-   qp=malloc(sizeof(uint32_t)*nPixels);
+   /* malloc check ok, using calloc for overflow */
+   qp=calloc(nPixels, sizeof(uint32_t));
    if (!qp) { goto error_4; }
 
-   avgDist=malloc(sizeof(uint32_t)*nPaletteEntries*nPaletteEntries);
+   if ((nPaletteEntries > SIZE_MAX / nPaletteEntries ) ||
+       (nPaletteEntries > SIZE_MAX / (nPaletteEntries * sizeof(uint32_t)))) {
+       goto error_5;
+   }
+   /* malloc check ok, using calloc for overflow, check of n*n above */
+   avgDist=calloc(nPaletteEntries*nPaletteEntries, sizeof(uint32_t));
    if (!avgDist) { goto error_5; }
 
-   avgDistSortKey=malloc(sizeof(uint32_t *)*nPaletteEntries*nPaletteEntries);
+   /* malloc check ok, using calloc for overflow, check of n*n above */
+   avgDistSortKey=calloc(nPaletteEntries*nPaletteEntries, sizeof(uint32_t *));
    if (!avgDistSortKey) { goto error_6; }
 
    if (!build_distance_tables(avgDist,avgDistSortKey,p,nPaletteEntries)) {
@@ -1399,8 +1417,9 @@ quantize2(Pixel *pixelData,
    uint32_t *qp;
    uint32_t *avgDist;
    uint32_t **avgDistSortKey;
-
-   p=malloc(sizeof(Pixel)*nQuantPixels);
+   
+   /* malloc check ok, using calloc */
+   p=calloc(nQuantPixels, sizeof(Pixel));
    if (!p) return 0;
    mean[0]=mean[1]=mean[2]=0;
    h=hashtable_new(unshifted_pixel_hash,unshifted_pixel_cmp);
@@ -1422,13 +1441,21 @@ quantize2(Pixel *pixelData,
    }
    hashtable_free(h);
 
-   qp=malloc(sizeof(uint32_t)*nPixels);
+   /* malloc check ok, using calloc */
+   qp=calloc(nPixels, sizeof(uint32_t));
    if (!qp) { goto error_1; }
 
-   avgDist=malloc(sizeof(uint32_t)*nQuantPixels*nQuantPixels);
+   if ((nQuantPixels > SIZE_MAX / nQuantPixels ) ||
+       (nQuantPixels > SIZE_MAX / (nQuantPixels * sizeof(uint32_t)))) {
+       goto error_2;
+   }
+
+   /* malloc check ok, using calloc for overflow, check of n*n above */
+   avgDist=calloc(nQuantPixels*nQuantPixels, sizeof(uint32_t));
    if (!avgDist) { goto error_2; }
 
-   avgDistSortKey=malloc(sizeof(uint32_t *)*nQuantPixels*nQuantPixels);
+   /* malloc check ok, using calloc for overflow, check of n*n above */
+   avgDistSortKey=calloc(nQuantPixels*nQuantPixels, sizeof(uint32_t *));
    if (!avgDistSortKey) { goto error_3; }
 
    if (!build_distance_tables(avgDist,avgDistSortKey,p,nQuantPixels)) {
@@ -1474,7 +1501,7 @@ ImagingQuantize(Imaging im, int colors, int mode, int kmeans)
     ImagingSectionCookie cookie;
 
     if (!im)
-	return ImagingError_ModeError();
+        return ImagingError_ModeError();
     if (colors < 1 || colors > 256)
         /* FIXME: for colors > 256, consider returning an RGB image
            instead (see @PIL205) */
@@ -1488,7 +1515,12 @@ ImagingQuantize(Imaging im, int colors, int mode, int kmeans)
     if (!strcmp(im->mode, "RGBA") && mode != 2 && mode != 3)
        return ImagingError_ModeError();
 
-    p = malloc(sizeof(Pixel) * im->xsize * im->ysize);
+    if ((im->xsize > SIZE_MAX / im->ysize) ||
+        (im->xsize > SIZE_MAX / (im->ysize * sizeof(Pixel)))) {
+        return ImagingError_MemoryError();
+    }
+    /* malloc check ok, using calloc for final overflow, x*y above */
+    p = calloc(im->xsize * im->ysize, sizeof(Pixel));
     if (!p)
         return ImagingError_MemoryError();
 
diff --git a/libImaging/QuantHeap.c b/libImaging/QuantHeap.c
index 9006903b7..2edf6d9cf 100644
--- a/libImaging/QuantHeap.c
+++ b/libImaging/QuantHeap.c
@@ -47,7 +47,12 @@ static int _heap_grow(Heap *h,int newsize) {
    void *newheap;
    if (!newsize) newsize=h->heapsize<<1;
    if (newsize<h->heapsize) return 0;
-   newheap=malloc(sizeof(void *)*newsize);
+   if (newsize > ((int)SIZE_MAX) / sizeof(void *)){
+       return 0;
+   }
+   /* malloc check ok, using calloc for overflow, also checking 
+      above due to memcpy below*/
+   newheap=calloc(newsize, sizeof(void *));
    if (!newheap) return 0;
    memcpy(newheap,h->heap,sizeof(void *)*h->heapsize);
    free(h->heap);
@@ -131,12 +136,17 @@ int ImagingQuantHeapTop(Heap *h,void **r) {
 
 Heap *ImagingQuantHeapNew(HeapCmpFunc cf) {
    Heap *h;
-
+   
+   /* malloc check ok, small constant allocation */
    h=malloc(sizeof(Heap));
    if (!h) return NULL;
    h->heapsize=INITIAL_SIZE;
-   h->heap=malloc(sizeof(void *)*h->heapsize);
-   if (!h->heap) { free(h); return NULL; }
+   /* malloc check ok, using calloc for overflow */
+   h->heap=calloc(h->heapsize, sizeof(void *));
+   if (!h->heap) { 
+       free(h); 
+       return NULL; 
+   }
    h->heapcount=0;
    h->cf=cf;
    return h;
diff --git a/libImaging/QuantOctree.c b/libImaging/QuantOctree.c
index cd0d7fbd1..3f61f0722 100644
--- a/libImaging/QuantOctree.c
+++ b/libImaging/QuantOctree.c
@@ -53,6 +53,7 @@ static ColorCube
 new_color_cube(int r, int g, int b, int a) {
    ColorCube cube;
 
+   /* malloc check ok, small constant allocation */
    cube = malloc(sizeof(struct _ColorCube));
    if (!cube) return NULL;
 
@@ -154,7 +155,11 @@ compare_bucket_count(const ColorBucket a, const ColorBucket b) {
 static ColorBucket
 create_sorted_color_palette(const ColorCube cube) {
    ColorBucket buckets;
-   buckets = malloc(sizeof(struct _ColorBucket)*cube->size);
+   if (cube->size > SIZE_MAX / sizeof(struct _ColorBucket)) {
+       return NULL;
+   }
+   /* malloc check ok, calloc + overflow check above for memcpy */
+   buckets = calloc(cube->size, sizeof(struct _ColorBucket));
    if (!buckets) return NULL;
    memcpy(buckets, cube->buckets, sizeof(struct _ColorBucket)*cube->size);
 
@@ -280,7 +285,15 @@ void add_lookup_buckets(ColorCube cube, ColorBucket palette, long nColors, long
 ColorBucket
 combined_palette(ColorBucket bucketsA, long nBucketsA, ColorBucket bucketsB, long nBucketsB) {
    ColorBucket result;
-   result = malloc(sizeof(struct _ColorBucket)*(nBucketsA+nBucketsB));
+   if (nBucketsA > SIZE_MAX - nBucketsB ||
+       (nBucketsA+nBucketsB) > SIZE_MAX / sizeof(struct _ColorBucket)) {
+       return NULL;
+   }
+   /* malloc check ok, overflow check above */
+   result = calloc(nBucketsA + nBucketsB, sizeof(struct _ColorBucket));
+   if (!result) {
+       return NULL;
+   }
    memcpy(result, bucketsA, sizeof(struct _ColorBucket) * nBucketsA);
    memcpy(&result[nBucketsA], bucketsB, sizeof(struct _ColorBucket) * nBucketsB);
    return result;
@@ -290,8 +303,9 @@ static Pixel *
 create_palette_array(const ColorBucket palette, unsigned int paletteLength) {
    Pixel *paletteArray;
    unsigned int i;
-
-   paletteArray = malloc(sizeof(Pixel)*paletteLength);
+   
+   /* malloc check ok, calloc for overflow */
+   paletteArray = calloc(paletteLength, sizeof(Pixel));
    if (!paletteArray) return NULL;
 
    for (i=0; i<paletteLength; i++) {
@@ -405,6 +419,7 @@ int quantize_octree(Pixel *pixelData,
    paletteBucketsFine = NULL;
    free(paletteBucketsCoarse);
    paletteBucketsCoarse = NULL;
+   if (!paletteBuckets) goto error;
 
    /* add all coarse colors to our coarse lookup cube. */
    coarseLookupCube = new_color_cube(cubeBits[4], cubeBits[5],
@@ -422,7 +437,8 @@ int quantize_octree(Pixel *pixelData,
    add_lookup_buckets(lookupCube, paletteBuckets, nFineColors, nCoarseColors);
 
    /* create result pixels and map palette indices */
-   qp = malloc(sizeof(Pixel)*nPixels);
+   /* malloc check ok, calloc for overflow */
+   qp = calloc(nPixels, sizeof(Pixel));
    if (!qp) goto error;
    map_image_pixels(pixelData, nPixels, lookupCube, qp);
 
diff --git a/libImaging/RankFilter.c b/libImaging/RankFilter.c
index 855e471d4..51f64611d 100644
--- a/libImaging/RankFilter.c
+++ b/libImaging/RankFilter.c
@@ -59,6 +59,12 @@ ImagingRankFilter(Imaging im, int size, int rank)
 
     if (!(size & 1))
         return (Imaging) ImagingError_ValueError("bad filter size");
+    
+    /* malloc check ok, for overflow in the define below */
+    if (size > SIZE_MAX / size || 
+        size > SIZE_MAX / (size * sizeof(FLOAT32))) {
+        return (Imaging) ImagingError_ValueError("filter size too large");
+    }
 
     size2 = size * size;
     margin = (size-1) / 2;
diff --git a/libImaging/Storage.c b/libImaging/Storage.c
index 4450d14e4..5968ad7a1 100644
--- a/libImaging/Storage.c
+++ b/libImaging/Storage.c
@@ -306,6 +306,7 @@ ImagingNewArray(const char *mode, int xsize, int ysize)
 
     /* Allocate image as an array of lines */
     for (y = 0; y < im->ysize; y++) {
+        /* malloc check UNDONE - where is linesize set? */
         p = (char *) malloc(im->linesize);
         if (!p) {
             ImagingDestroyArray(im);
@@ -345,18 +346,23 @@ ImagingNewBlock(const char *mode, int xsize, int ysize)
     if (!im)
         return NULL;
 
-    /* Use a single block */
-    bytes = (Py_ssize_t) im->ysize * im->linesize;
+
+    if (im->linesize &&
+        im->ysize > SIZE_MAX / im->linesize) {
+        /* punt if we're going to overflow */
+        return NULL;
+    }
+    /* Use a single block */        
+    bytes = ((Py_ssize_t) im->ysize) * im->linesize;
     if (bytes <= 0)
         /* some platforms return NULL for malloc(0); this fix
            prevents MemoryError on zero-sized images on such
            platforms */
         bytes = 1;
-    im->block = (char *) malloc(bytes);
+    /* malloc check ok, overflow check above */
+    im->block = (char *) calloc(bytes, 1);
 
     if (im->block) {
-        memset(im->block, 0, bytes);
-
         for (y = i = 0; y < im->ysize; y++) {
             im->image[y] = im->block + i;
             i += im->linesize;
@@ -392,7 +398,7 @@ ImagingNew(const char* mode, int xsize, int ysize)
     } else
         bytes = strlen(mode); /* close enough */
 
-    if ((int64_t) xsize * (int64_t) ysize * bytes <= THRESHOLD) {
+    if ((int64_t) xsize * (int64_t) ysize <= THRESHOLD / bytes) {
         im = ImagingNewBlock(mode, xsize, ysize);
         if (im)
             return im;
diff --git a/libImaging/TiffDecode.c b/libImaging/TiffDecode.c
index b9b61e48f..3df48c7ba 100644
--- a/libImaging/TiffDecode.c
+++ b/libImaging/TiffDecode.c
@@ -305,6 +305,7 @@ int ImagingLibTiffEncodeInit(ImagingCodecState state, char *filename, int fp) {
 	} else {
 		// malloc a buffer to write the tif, we're going to need to realloc or something if we need bigger.
 		TRACE(("Opening a buffer for writing \n"));
+        /* malloc check ok, small constant allocation */
 		clientstate->data = malloc(bufsize);
 		clientstate->size = bufsize;
 		clientstate->flrealloc=1;
diff --git a/libImaging/ZipDecode.c b/libImaging/ZipDecode.c
index 96c8b21bd..dfcfa36bb 100644
--- a/libImaging/ZipDecode.c
+++ b/libImaging/ZipDecode.c
@@ -56,9 +56,15 @@ ImagingZipDecode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
         if (context->mode == ZIP_PNG || context->mode == ZIP_PNG_PALETTE)
             context->prefix = 1; /* PNG */
 
+        /* overflow check for malloc */
+        if (state->bytes > SIZE_MAX - 1) {
+            state->errcode = IMAGING_CODEC_MEMORY;
+            return -1;
+        }
         /* Expand standard buffer to make room for the (optional) filter
            prefix, and allocate a buffer to hold the previous line */
         free(state->buffer);
+        /* malloc check ok, overflow checked above */
         state->buffer = (UINT8*) malloc(state->bytes+1);
         context->previous = (UINT8*) malloc(state->bytes+1);
         if (!state->buffer || !context->previous) {
diff --git a/libImaging/ZipEncode.c b/libImaging/ZipEncode.c
index 1e96aee71..7f50be9ed 100644
--- a/libImaging/ZipEncode.c
+++ b/libImaging/ZipEncode.c
@@ -37,9 +37,16 @@ ImagingZipEncode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
 
         /* Valid modes are ZIP_PNG, ZIP_PNG_PALETTE, and ZIP_TIFF */
 
+        /* overflow check for malloc */
+        if (state->bytes > SIZE_MAX - 1) {
+            state->errcode = IMAGING_CODEC_MEMORY;
+            return -1;
+        }
+        
         /* Expand standard buffer to make room for the filter selector,
            and allocate filter buffers */
         free(state->buffer);
+        /* malloc check ok, overflow checked above */
         state->buffer = (UINT8*) malloc(state->bytes+1);
         context->previous = (UINT8*) malloc(state->bytes+1);
         context->prior = (UINT8*) malloc(state->bytes+1);