Commit 49921f2c authored Sep 08, 2016 by songjinshi Committed by 金时宋 Sep 20, 2016

[AssetManager]:Fix thread race caused double free issue.

The SharedZip's Asset is not thread-safety,the getResourceTableAsset()
and setResourceTableAsset(Asset* asset) function of the SharedZip is
not sync with a same lock.

Consider the following sequence of events:
Thread A calls setResourceTableAsset(Asset* asset),it will set
mResourceTableAsset = asset; then to calls getBuffer() of the asset.
Thread B calls getResourceTableAsset(),which return mResourceTableAsset,
then to calls getBuffer() of the mResourceTableAsset,the asset and
mResourceTableAsset is same one object.
Thread A to delete mZipInflater in getBuffer().
Thread B to delete mZipInflater in getBuffer().

It will cause crash becuase double delete mZipInflater in getBuffer().

https://code.google.com/p/android/issues/detail?id=211941



Change-Id: I5a7d67fdf64c4aa03f505b37a2fa840f4443d158
Signed-off-by: songjinshi <songjinshi@xiaomi.com>

parent 0027ddf9

libs/androidfw/AssetManager.cpp

+2 −1

Original line number	Diff line number	Diff line
		@@ -1892,6 +1892,7 @@ ZipFileRO* AssetManager::SharedZip::getZip()

		Asset* AssetManager::SharedZip::getResourceTableAsset()
		{
		AutoMutex _l(gLock);
		ALOGV("Getting from SharedZip %p resource asset %p\n", this, mResourceTableAsset);
		return mResourceTableAsset;
		}
		@@ -1901,10 +1902,10 @@ Asset* AssetManager::SharedZip::setResourceTableAsset(Asset* asset)
		{
		AutoMutex _l(gLock);
		if (mResourceTableAsset == NULL) {
		mResourceTableAsset = asset;
		// This is not thread safe the first time it is called, so
		// do it here with the global lock held.
		asset->getBuffer(true);
		mResourceTableAsset = asset;
		return asset;
		}
		}