Bug 1441941 - Limit allocations in SkTDArray. r=jrmuizel, a=RyanVM

gfx/skia/skia/include/core/SkTypes.h

@@ -109,6 +109,11 @@ SK_API extern void* sk_calloc(size_t size);
  */
 SK_API extern void* sk_calloc_throw(size_t size);
 
+// Performs a safe multiply count * elemSize, checking for overflow
+SK_API extern void* sk_calloc_throw(size_t count, size_t elemSize);
+SK_API extern void* sk_malloc_throw(size_t count, size_t elemSize);
+SK_API extern void* sk_realloc_throw(void* buffer, size_t count, size_t elemSize);
+
 // bzero is safer than memset, but we can't rely on it, so... sk_bzero()
 static inline void sk_bzero(void* buffer, size_t size) {
     // Please c.f. sk_careful_memcpy.  It's undefined behavior to call memset(null, 0, 0).
@@ -295,6 +300,7 @@ template <typename D, typename S> D SkTo(S s) {
 #define SK_MaxU32   0xFFFFFFFF
 #define SK_MinU32   0
 #define SK_NaN32    ((int) (1U << 31))
+#define SK_MaxSizeT SIZE_MAX
 
 /** Returns true if the value can be represented with signed 16bits
  */

gfx/skia/skia/include/private/SkTDArray.h

@@ -21,7 +21,7 @@ public:
         fReserve = fCount = 0;
         fArray = NULL;
         if (count) {
-            fArray = (T*)sk_malloc_throw(count * sizeof(T));
+            fArray = (T*)sk_malloc_throw(count, sizeof(T));
             memcpy(fArray, src, sizeof(T) * count);
             fReserve = fCount = count;
         }
@@ -346,7 +346,7 @@ public:
 
     void shrinkToFit() {
         fReserve = fCount;
-        fArray = (T*)sk_realloc_throw(fArray, fReserve * sizeof(T));
+        fArray = (T*)sk_realloc_throw(fArray, fReserve, sizeof(T));
     }
 
 private:
@@ -359,6 +359,7 @@ private:
      *  This is the same as calling setCount(count() + delta).
      */
     void adjustCount(int delta) {
+        SkASSERT_RELEASE(fCount <= std::numeric_limits<int>::max() - delta);
         this->setCount(fCount + delta);
     }
 
@@ -372,9 +373,10 @@ private:
      */
     void resizeStorageToAtLeast(int count) {
         SkASSERT(count > fReserve);
+        SkASSERT_RELEASE(count <= std::numeric_limits<int>::max() - std::numeric_limits<int>::max() / 5 - 4);
         fReserve = count + 4;
         fReserve += fReserve / 4;
-        fArray = (T*)sk_realloc_throw(fArray, fReserve * sizeof(T));
+        fArray = (T*)sk_realloc_throw(fArray, fReserve, sizeof(T));
     }
 };
 

gfx/skia/skia/src/core/SkMallocPixelRef.cpp

@@ -8,8 +8,21 @@
 #include "SkMallocPixelRef.h"
 #include "SkBitmap.h"
 #include "SkReadBuffer.h"
+#include "SkSafeMath.h"
 #include "SkWriteBuffer.h"
 
+void* sk_calloc_throw(size_t count, size_t elemSize) {
+    return sk_calloc_throw(SkSafeMath::Mul(count, elemSize));
+}
+
+void* sk_malloc_throw(size_t count, size_t elemSize) {
+    return sk_malloc_throw(SkSafeMath::Mul(count, elemSize));
+}
+
+void* sk_realloc_throw(void* buffer, size_t count, size_t elemSize) {
+    return sk_realloc_throw(buffer, SkSafeMath::Mul(count, elemSize));
+}
+
 // assumes ptr was allocated via sk_malloc
 static void sk_free_releaseproc(void* ptr, void*) {
     sk_free(ptr);

gfx/skia/skia/src/core/SkMath.cpp

@@ -84,3 +84,18 @@ float SkScalarSinCos(float radians, float* cosValue) {
     }
     return sinValue;
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+size_t SkSafeMath::Add(size_t x, size_t y) {
+    SkSafeMath tmp;
+    size_t sum = tmp.add(x, y);
+    return tmp.ok() ? sum : SK_MaxSizeT;
+}
+
+size_t SkSafeMath::Mul(size_t x, size_t y) {
+    SkSafeMath tmp;
+    size_t prod = tmp.mul(x, y);
+    return tmp.ok() ? prod : SK_MaxSizeT;
+}
+

gfx/skia/skia/src/core/SkSafeMath.h

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkSafeMath_DEFINED
+#define SkSafeMath_DEFINED
+
+#include "SkTypes.h"
+
+// SkSafeMath always check that a series of operations do not overflow.
+// This must be correct for all platforms, because this is a check for safety at runtime.
+
+class SkSafeMath {
+public:
+    SkSafeMath() = default;
+
+    bool ok() const { return fOK; }
+    explicit operator bool() const { return fOK; }
+
+    size_t mul(size_t x, size_t y) {
+        return sizeof(size_t) == sizeof(uint64_t) ? mul64(x, y) : mul32(x, y);
+    }
+
+    size_t add(size_t x, size_t y) {
+        size_t result = x + y;
+        fOK &= result >= x;
+        return result;
+    }
+
+    /**
+     *  Return a + b, unless this result is an overflow/underflow. In those cases, fOK will
+     *  be set to false, and it is undefined what this returns.
+     */
+    int addInt(int a, int b) {
+        if (b < 0 && a < std::numeric_limits<int>::min() - b) {
+            fOK = false;
+            return a;
+        } else if (b > 0 && a > std::numeric_limits<int>::max() - b) {
+            fOK = false;
+            return a;
+        }
+        return a + b;
+    }
+
+    size_t alignUp(size_t x, size_t alignment) {
+        SkASSERT(alignment && !(alignment & (alignment - 1)));
+        return add(x, alignment - 1) & ~(alignment - 1);
+    }
+
+    template <typename T> T castTo(size_t value) {
+        if (!SkTFitsIn<T>(value)) {
+            fOK = false;
+        }
+        return static_cast<T>(value);
+    }
+
+    // These saturate to their results
+    static size_t Add(size_t x, size_t y);
+    static size_t Mul(size_t x, size_t y);
+    static size_t Align4(size_t x) {
+        SkSafeMath safe;
+        return safe.alignUp(x, 4);
+    }
+
+private:
+    uint32_t mul32(uint32_t x, uint32_t y) {
+        uint64_t bx = x;
+        uint64_t by = y;
+        uint64_t result = bx * by;
+        fOK &= result >> 32 == 0;
+        return result;
+    }
+
+    uint64_t mul64(uint64_t x, uint64_t y) {
+        if (x <= std::numeric_limits<uint64_t>::max() >> 32
+            && y <= std::numeric_limits<uint64_t>::max() >> 32) {
+            return x * y;
+        } else {
+            auto hi = [](uint64_t x) { return x >> 32; };
+            auto lo = [](uint64_t x) { return x & 0xFFFFFFFF; };
+
+            uint64_t lx_ly = lo(x) * lo(y);
+            uint64_t hx_ly = hi(x) * lo(y);
+            uint64_t lx_hy = lo(x) * hi(y);
+            uint64_t hx_hy = hi(x) * hi(y);
+            uint64_t result = 0;
+            result = this->add(lx_ly, (hx_ly << 32));
+            result = this->add(result, (lx_hy << 32));
+            fOK &= (hx_hy + (hx_ly >> 32) + (lx_hy >> 32)) == 0;
+
+            #if defined(SK_DEBUG) && defined(__clang__) && defined(__x86_64__)
+                auto double_check = (unsigned __int128)x * y;
+                SkASSERT(result == (double_check & 0xFFFFFFFFFFFFFFFF));
+                SkASSERT(!fOK || (double_check >> 64 == 0));
+            #endif
+
+            return result;
+        }
+    }
+    bool fOK = true;
+};
+
+#endif//SkSafeMath_DEFINED