Iphone 崩溃：iOS 6代码的UIImage样式崩溃？

下面是我为图像设计样式的代码。在iOS4.3及以上版本中，代码工作正常，但在ios6中，代码崩溃

-(UIImage *)grayImage:(UIImage *)image
{
    CGImageRef img= image.CGImage;//imageSelected.CGImage;//self.originalPhoto.CGImage;

    CFDataRef dataref=CGDataProviderCopyData(CGImageGetDataProvider(img));

    int length=CFDataGetLength(dataref);
    UInt8 *data=(UInt8 *)CFDataGetBytePtr(dataref);

    for(int index=0;index<length;index+=4){
        Byte grayScale =
        (Byte)(data[index+3]*.11  +
               data[index + 2] * .59  +
               data[index + 1] * .3);

        //set the new image's pixel to the grayscale version
        data[index+1] = grayScale;// Code Crash here , By SIGABRAT (Exe_Bad_Access)
        data[index+2] = grayScale;
        data[index+3] = grayScale;
    }
    // .. Take image attributes
    size_t width=CGImageGetWidth(img);
    size_t height=CGImageGetHeight(img);
    size_t bitsPerComponent=CGImageGetBitsPerComponent(img);
    size_t bitsPerPixel=CGImageGetBitsPerPixel(img);
    size_t bytesPerRow=CGImageGetBytesPerRow(img);

    // .. Do the pixel manupulation
    CGColorSpaceRef colorspace=CGImageGetColorSpace(img);
    CGBitmapInfo bitmapInfo=CGImageGetBitmapInfo(img);
    CFDataRef newData=CFDataCreate(NULL,data,length);
    CGDataProviderRef provider=CGDataProviderCreateWithCFData(newData);

    // .. Get the Image out of this raw data
    CGImageRef newImg=CGImageCreate(width,height,bitsPerComponent,bitsPerPixel,bytesPerRow,colorspace,bitmapInfo,provider,NULL,true,kCGRenderingIntentDefault);

    // .. Prepare the image from raw data
    UIImage* rawImage = [[UIImage alloc] initWithCGImage:newImg] ;

    // .. done with all,so release the references
    CFRelease(newData);
    CGImageRelease(newImg);
    CGDataProviderRelease(provider);
    CFRelease(dataref);

    return rawImage;

}

-（UIImage*）灰度图像：（UIImage*）图像
{
CGImageRef img=image.CGImage；//imageSelected.CGImage；//self.originalPhoto.CGImage；
CFDataRef dataref=CGDataProviderCopyData（CGImageGetDataProvider（img））；
int length=CFDataGetLength（dataref）；
UInt8*数据=（UInt8*）CFDataGetBytePtr（dataref）；
对于（int index=0；index请使用CFMutableDataRef代替CFDataRef，如下所示

CFDataRef m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage)); 
//->write this:
CFMutableDataRef m_DataRef = CFDataCreateMutableCopy(0, 0, CGDataProviderCopyData(CGImageGetDataProvider(inImage)));

UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef); 
//->write this
UInt8 *m_PixelBuf=(UInt8 *)CFDataGetMutableBytePtr(m_DataRef);

崩溃后报告plz？？你为什么要双重解除对指针的引用？我已经检查过了，但在iOS6模拟器中它没有崩溃。这个崩溃是在设备上发生的。请看屏幕截图。我正在模拟器和iPad上运行此代码，在这两种情况下，它都是在同一阶段崩溃的。我不明白为什么会出现EXE_BAD_访问。