AuroraMiddleware/skia2
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Fix buffer overrun, bit overrun and add a test.

Browse Source 
BUG=539691

Review URL: https://codereview.chromium.org/1453163002
This commit is contained in:
herb 2015-11-18 10:50:33 -08:00 committed by Commit bot
parent 988adddd48
commit 5520dede29
2 changed files with 111 additions and 40 deletions
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86
src/core/SkBlitter.cpp
View File

@ -83,18 +83,18 @@ void SkBlitter::blitAntiRect(int x, int y, int width, int height,
static inline void bits_to_runs(SkBlitter* blitter, int x, int y,
const uint8_t bits[],
U8CPU left_mask, int rowBytes,
U8CPU right_mask) {
uint8_t left_mask, ptrdiff_t rowBytes,
uint8_t right_mask) {
int inFill = 0;
int pos = 0;
while (--rowBytes >= 0) {
unsigned b = *bits++ & left_mask;
uint8_t b = *bits++ & left_mask;
if (rowBytes == 0) {
b &= right_mask;
}
for (unsigned test = 0x80; test != 0; test >>= 1) {
for (uint8_t test = 0x80U; test != 0; test >>= 1) {
if (b & test) {
if (!inFill) {
pos = x;
@ -108,7 +108,7 @@ static inline void bits_to_runs(SkBlitter* blitter, int x, int y,
}
x += 1;
}
left_mask = 0xFF;
left_mask = 0xFFU;
}
// final cleanup
@ -117,6 +117,11 @@ static inline void bits_to_runs(SkBlitter* blitter, int x, int y,
}
}
// maskBitCount is the number of 1's to place in the mask. It must be in the range between 1 and 8.
static uint8_t generate_right_mask(int maskBitCount) {
return static_cast<uint8_t>(0xFF00U >> maskBitCount);
}
void SkBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
SkASSERT(mask.fBounds.contains(clip));
@ -124,54 +129,55 @@ void SkBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
int cx = clip.fLeft;
int cy = clip.fTop;
int maskLeft = mask.fBounds.fLeft;
int mask_rowBytes = mask.fRowBytes;
int maskRowBytes = mask.fRowBytes;
int height = clip.height();
const uint8_t* bits = mask.getAddr1(cx, cy);
SkDEBUGCODE(const uint8_t* endOfImage =
mask.fImage + (mask.fBounds.height() - 1) * maskRowBytes
+ ((mask.fBounds.width() + 7) >> 3));
if (cx == maskLeft && clip.fRight == mask.fBounds.fRight) {
while (--height >= 0) {
bits_to_runs(this, cx, cy, bits, 0xFF, mask_rowBytes, 0xFF);
bits += mask_rowBytes;
int affectedRightBit = mask.fBounds.width() - 1;
ptrdiff_t rowBytes = (affectedRightBit >> 3) + 1;
SkASSERT(bits + rowBytes <= endOfImage);
U8CPU rightMask = generate_right_mask((affectedRightBit & 7) + 1);
bits_to_runs(this, cx, cy, bits, 0xFF, rowBytes, rightMask);
bits += maskRowBytes;
cy += 1;
}
} else {
int left_edge = cx - maskLeft;
SkASSERT(left_edge >= 0);
int rite_edge = clip.fRight - maskLeft;
SkASSERT(rite_edge > left_edge);
// Bits is calculated as the offset into the mask at the point {cx, cy} therfore, all
// addressing into the bit mask is relative to that point. Since this is an address
// calculated from a arbitrary bit in that byte, calculate the left most bit.
int bitsLeft = cx - ((cx - maskLeft) & 7);
int left_mask = 0xFF >> (left_edge & 7);
int rite_mask = 0xFF << (8 - (rite_edge & 7));
int full_runs = (rite_edge >> 3) - ((left_edge + 7) >> 3);
// Everything is relative to the bitsLeft.
int leftEdge = cx - bitsLeft;
SkASSERT(leftEdge >= 0);
int rightEdge = clip.fRight - bitsLeft;
SkASSERT(rightEdge > leftEdge);
// check for empty right mask, so we don't read off the end (or go slower than we need to)
if (rite_mask == 0) {
SkASSERT(full_runs >= 0);
full_runs -= 1;
rite_mask = 0xFF;
}
if (left_mask == 0xFF) {
full_runs -= 1;
}
// Calculate left byte and mask
const uint8_t* leftByte = bits;
U8CPU leftMask = 0xFFU >> (leftEdge & 7);
// back up manually so we can keep in sync with our byte-aligned src
// have cx reflect our actual starting x-coord
cx -= left_edge & 7;
// Calculate right byte and mask
int affectedRightBit = rightEdge - 1;
const uint8_t* rightByte = bits + (affectedRightBit >> 3);
U8CPU rightMask = generate_right_mask((affectedRightBit & 7) + 1);
if (full_runs < 0) {
SkASSERT((left_mask & rite_mask) != 0);
while (--height >= 0) {
bits_to_runs(this, cx, cy, bits, left_mask, 1, rite_mask);
bits += mask_rowBytes;
cy += 1;
}
} else {
while (--height >= 0) {
bits_to_runs(this, cx, cy, bits, left_mask, full_runs + 2, rite_mask);
bits += mask_rowBytes;
cy += 1;
}
// leftByte and rightByte are byte locations therefore, to get a count of bytes the
// code must add one.
ptrdiff_t rowBytes = rightByte - leftByte + 1;
while (--height >= 0) {
SkASSERT(bits + rowBytes <= endOfImage);
bits_to_runs(this, bitsLeft, cy, bits, leftMask, rowBytes, rightMask);
bits += maskRowBytes;
cy += 1;
}
}
} else {

65
tests/BlitMaskClip.cpp Normal file
View File

@ -0,0 +1,65 @@
/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkBlitter.h"
#include "SkMask.h"
#include "Test.h"
class TestBlitter : public SkBlitter {
public:
TestBlitter(SkIRect bounds, skiatest::Reporter* reporter)
: fBounds(bounds)
, fReporter(reporter) { }
void blitH(int x, int y, int width) override {
REPORTER_ASSERT(fReporter, x >= fBounds.fLeft && x < fBounds.fRight);
REPORTER_ASSERT(fReporter, y >= fBounds.fTop && y < fBounds.fBottom);
int right = x + width;
REPORTER_ASSERT(fReporter, right > fBounds.fLeft && right <= fBounds.fRight);
}
private:
SkIRect fBounds;
skiatest::Reporter* fReporter;
};
// Exercise all clips compared with different widths of bitMask. Make sure that no buffer
// overruns happen.
DEF_TEST(BlitAndClip, reporter) {
const int originX = 100;
const int originY = 100;
for (int width = 1; width <= 32; width++) {
const int height = 2;
int rowBytes = (width + 7) >> 3;
uint8_t* bits = new uint8_t[rowBytes * height];
SkIRect b = {originX, originY, originX + width, originY + height};
SkMask mask;
mask.fFormat = SkMask::kBW_Format;
mask.fBounds = b;
mask.fImage = (uint8_t*)bits;
mask.fRowBytes = rowBytes;
TestBlitter tb(mask.fBounds, reporter);
for (int top = b.fTop; top < b.fBottom; top++) {
for (int bottom = top + 1; bottom <= b.fBottom; bottom++) {
for (int left = b.fLeft; left < b.fRight; left++) {
for (int right = left + 1; right <= b.fRight; right++) {
SkIRect clipRect = {left, top, right, bottom};
tb.blitMask(mask, clipRect);
}
}
}
}
delete [] bits;
}
}