From cd82440ec714979543a5b5351f4ec96a467ee0de Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Wed, 16 Sep 2015 23:54:29 -0700
Subject: [PATCH] VP8LAllocateHistogramSet: align histogram[] entries

fixes issue #262: a SIGBUS when accessing a misaligned double in
VP8LHistogram

Change-Id: Ic78cc5366d7e43d892c375b6a69dce2379db931b
---
 src/enc/histogram.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/enc/histogram.c b/src/enc/histogram.c
index 98a6e80d..15aea271 100644
--- a/src/enc/histogram.c
+++ b/src/enc/histogram.c
@@ -20,6 +20,9 @@
 #include "../dsp/lossless.h"
 #include "../utils/utils.h"
 
+#define ALIGN_CST 15
+#define DO_ALIGN(PTR) ((uintptr_t)((PTR) + ALIGN_CST) & ~ALIGN_CST)
+
 #define MAX_COST 1.e38
 
 // Number of partitions for the three dominant (literal, red and blue) symbol
@@ -110,9 +113,9 @@ VP8LHistogram* VP8LAllocateHistogram(int cache_bits) {
 VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) {
   int i;
   VP8LHistogramSet* set;
-  const size_t total_size = sizeof(*set)
-                            + sizeof(*set->histograms) * size
-                            + (size_t)VP8LGetHistogramSize(cache_bits) * size;
+  const int histo_size = VP8LGetHistogramSize(cache_bits);
+  const size_t total_size =
+      sizeof(*set) + size * (sizeof(*set->histograms) + histo_size + ALIGN_CST);
   uint8_t* memory = (uint8_t*)WebPSafeMalloc(total_size, sizeof(*memory));
   if (memory == NULL) return NULL;
 
@@ -123,12 +126,12 @@ VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) {
   set->max_size = size;
   set->size = size;
   for (i = 0; i < size; ++i) {
+    memory = (uint8_t*)DO_ALIGN(memory);
     set->histograms[i] = (VP8LHistogram*)memory;
     // literal_ won't necessary be aligned.
     set->histograms[i]->literal_ = (uint32_t*)(memory + sizeof(VP8LHistogram));
     VP8LHistogramInit(set->histograms[i], cache_bits);
-    // There's no padding/alignment between successive histograms.
-    memory += VP8LGetHistogramSize(cache_bits);
+    memory += histo_size;
   }
   return set;
 }