Bug 279221 – REGRESSION(276827@main): Possible null pointer dereferencing when an image frame finishes decoding while the document is getting closed

• Component: Images
• Status: RESOLVED FIXED

[Said Abou-Hallawa]

Before 276827@main, the image decoding thread was calling ImageSource::cachePlatformImageAtIndexAsync() on the main thread to cache the decoded frame. This function was making an early return if isDecoderAvailable() is not available.

void ImageSource::cachePlatformImageAtIndexAsync(...)
{
    if (!isDecoderAvailable())
        return;
    ...
}

After 276827@main, the image decoding thread calls BitmapImageSource::imageFrameDecodeAtIndexHasFinished() which calls BitmapImageSource::cacheMetadataAtIndex(). This function assumes the decoder has to be available:

void BitmapImageSource::cacheMetadataAtIndex(...)
{
    ASSERT(m_decoder);
    ...
}

We need to restore the old check back to avoid null pointer dereferencing if the document is getting closed.

[Said Abou-Hallawa]

rdar://133487516

[Said Abou-Hallawa]

Pull request: https://github.com/WebKit/WebKit/pull/33207

[EWS]

Committed 283241@main (926b6385eb9e): <https://commits.webkit.org/283241@main>

Reviewed commits have been landed. Closing PR #33207 and removing active labels.