Posted by Eddie Hsu (Technical Program Manager), Brent VerWeyst (Product Manager), Maya Ben Ari (Product Manager), Amith Dsouza (Technical Account Manager), Iliyan Malchev (Project Treble Architect)
Over the past few years we’ve introduced new capabilities that enable us to deliver updates more uniformly, quickly, and efficiently to Android devices. These capabilities include:
Thanks to these efforts, the adoption of Android 10 has been faster than any previous versions of Android. Android 10 was running on 100 million devices 5 months post launch – 28% faster than Android Pie.
Below are the major themes in updatability this year:
OEM Developer Previews: In Android 11, device makers (OEMs) are continuing their developer previews ahead of the official launch. Seven OEMs have released Developer Preview builds on 13 devices to provide app developers with diverse hardware as they test for compatibility.
Google Play system update: 21 OS components are now updatable, including 9 additions in Android 11 focused on improving privacy, security, and developer consistency across devices. Highlights include an enhanced permissions component that standardizes user and developer access to critical privacy controls on Android devices, a Neural Networks API (NNAPI) component that optimizes performance and guarantees consistent APIs across devices, and a Tethering component for improved interoperability. The new updatable OS components in Android 11 are: Tethering, NNAPI, Cell Broadcast Receiver, adbd, Internet Key Exchange, Media Provider, statsd, WiFi, and SDK extension.
Generic Kernel Image: Our ongoing updatability work extends to the Linux kernel itself, with initiatives such as 6-year LTS support. In Android 11, we are further isolating common code in the Android Linux kernel to create a Generic Kernel Image (GKI) that works across all Android devices, as well as to enable faster security deployments. Stay tuned for a more detailed post on GKI in the coming months.
Virtual A/B: Most OS updates are not delivered via Google Play. Instead, they use separate third-party Over-the-Air (OTA) services that differ among the various OEMs. These services use a mechanism that, while very space efficient, has the disadvantage of being slow to apply, rendering the device inoperable for the duration. To solve this problem, in Android Nougat we launched a mechanism called "A/B OTA" (aka Seamless Updates). A/B OTAs have the advantage of appearing to be near-instant from the user's perspective, since they apply in the background and become active on the next reboot. However, they doubled the amount of storage reserved for the OS itself, limiting adoption among OEMs.
We’ve developed a new OTA mechanism – Virtual A/B – that combines the benefits of the previous two: being seamless from the user's perspective while requiring less storage. We are working closely with our OEM partners to begin implementing Virtual A/B in Android 11 devices, making OTAs as frictionless as possible. Going forward, Virtual A/B will be the only supported OTA mechanism in Android.
We’re excited by the increased adoption of Android and are grateful for the close collaborations with our chipset and OEM partners to deploy updates earlier. We continue to work on a number of enhancements in the platform and infrastructure to make it easier for developers and users to benefit from the latest versions of Android.
Reminder that the Android engineering team will host a Reddit AMA today at 12:00PM PST to answer your technical questions about Android 11. See this post for details and to submit your questions.
Posted by Dave Burke, VP of Engineering
A few weeks ago we unwrapped the first Beta of Android 11 with a focus on people, controls, and privacy. As we highlighted in the #Android11Beta Launch, we’re making Android more people-centric and expressive, helping users control their smart devices, and giving them even more control over sensitive permissions. Developers can use APIs like Conversations, Bubbles, Device Controls, and Media Controls, to integrate these experiences into their apps.
Today we’re pushing out the second Beta of Android 11 for you to try. This release takes us to the Platform Stability milestone, which means that Android 11’s APIs and behaviors are finalized. For developers, it’s time to get started on your final compatibility updates and publish them in time for the official release later in Q3.
This week’s theme in #11 Weeks of Android is Android 11 Compatibility and we’ll be sharing helpful content and materials all week. You can find them on the #11 Weeks page or follow Android Developers on Twitter and Youtube.
You can get Beta 2 today on your Pixel 2, 3, 3a, and 4 device by enrolling here for over-the-air updates, and downloads are also available. If you previously enrolled for Beta 1, you will automatically get the over-the-air update. Let us know what you think, and thanks for the feedback you’ve provided so far!
Beta 2 brings Android 11 to Platform Stability, a new release milestone that we added this year just for developers, based on your feedback.
Platform Stability means that all app-facing surfaces and behaviors are now final in Android 11. This includes not only final SDK and NDK APIs, but also final system behaviors and restrictions on non-SDK interfaces that may affect apps. So from Beta 2, you can release compatibility updates with confidence that the platform won’t change. More on the timeline is here.
With the platform now stable, we’re encouraging all app and game developers to start your final compatibility testing and publish your updates ahead of the final release.
For all SDK, library, tools, and game engine developers, it’s even more important to start testing now and release your compatible updates as soon as possible -- your downstream app and game developers may be blocked until they receive your updates. When you’ve released a compatible update, be vocal and let developers know!
For Android, the term app compatibility means that your app runs properly on a specific version of the platform, typically the latest version. You can check this right now by installing your production app on a device or emulator running Android 11. Just test all of the user flows and features, and if the app looks and runs properly, then you’re done, it’s compatible!
It sounds simple, but sometimes there’s more to it. With each release, we make integral changes that improve privacy and security, as well as implement changes that evolve the overall user experience across the OS. Sometimes these can affect your apps, so it’s important to take a look at the behavior changes and test against them, then publish the compatible update to users. It’s a basic but critical level of quality.
App compatibility comes into play as users update to the latest version of Android, whether they’ve purchased a new device or installed an update on their current device. They’re excited to explore the latest version of Android, and they want to experience it with their favorite apps. If the apps don’t work properly, it’s a major issue - for users and for all of us.
So while there are a ton of new APIs and capabilities to explore, and more changes to consider when you’re ready to change your app’s targeting, start by testing your current app and releasing a compatible update first.
Updates to Pixel and other devices will get started as soon as Android 11 reaches the final release to Android Open Source Project (AOSP), which we expect later in Q3. Multiple partner devices are also in active public previews now to support your compatibility testing.
With each release, we’re working to reduce the work you’ll need to do to get your apps ready. In Android 11, we’ve added new processes, developer tools, and release milestones to minimize the impact of platform updates and make it easier for apps to stay compatible.
App compatibility toggles in Developer options.
Now that Android 11 is stable, make your apps compatible as soon as possible. Here’s how to do it.
For testing your current app, start with the behavior changes for all apps to see where it could be affected. Here are the top changes (these apply regardless of your app’s targetSdkVersion):
Remember to test the libraries and SDKs in your app for compatibility. If you find an issue, try updating to the latest version of the SDK, or reach out to the developer for help.
Later, after you’ve published the compatible version of your current app, you can start the process of updating your app's targetSdkVersion. Review the behavior changes for Android 11 apps and try the compatibility framework to help find impacts. Here are some of the top changes to test for (these apply only to targetSdkVersion 30+):
During testing, watch for uses of restricted non-SDK interfaces in your app and move those to public SDK equivalents instead. You can read about the restricted APIs here.
As soon as you’re ready, dive into Android 11 and learn about the new experiences you can build. Our #Android11 Beta post has a recap of new features for developers, and you can also visit the Beta Launch page to see talks from the Android team on what’s new in their areas.
Android Studio also has new features for Android 11 also, to improve your productivity and workflow, such as ADB incremental for faster installs of large APKs, and additional nullability annotations on platform APIs. You can give these a try by downloading the latest Android Studio Beta or Canary version. Instructions for configuring Android Studio for Android 11 are here.
For complete details on Android 11 features and APIs, visit the Android 11 developer site.
It’s easy! You can enroll here to get Android 11 Beta updates over-the-air for Pixel 2, 3, 3a, and 4 devices. Alternatively, give Android Flash Tool a try for easy on-demand updates, and downloadable system images are also available. If you don't have a Pixel device, you can use the Android Emulator in Android Studio or try a GSI image to run Android 11 on supported Treble-compliant devices.
As always, your feedback is critical, so please let us know what you think. You can use our hotlists for filing platform issues (including privacy and behavior changes), app compatibility issues, and third-party SDK issues. You've shared great feedback with us so far -- thank you!
This week in #11 Weeks of Android, we’re highlighting Android 11 Compatibility, a theme that’s important for all developers now that the platform has reached stability.
We’re sharing resources to help you with compatibility testing here, and you can follow Android Developers on Twitter and Youtube to catch helpful content and materials in this area all this week!
Also, the Android engineering team will host a Reddit AMA on r/androiddev tomorrow, July 9 at 12:00PM PST, to answer your technical questions about Android 11. See this post for details and to submit your questions.
This blogpost is a collaboration between Google and Excelliance Tech. Authored by Zhuo Chen with support from Zhihai Wang, Gao Huang from Excelliance Tech.
Excelliance Tech improved the stability and compatibility of their LeBian SDK by moving away from non-SDK APIs, toward stable, official APIs. Their collaboration with the Android team during the process also led to a new public API for resource loading that all developers can use - the ResourcesLoader API in Android 11.
Games are becoming increasingly complex, and a loading progress bar is not only a countdown to a new adventure, but also a bridge which connects players and developers.
Players want the game to load right away, so "loading" has its own priorities: resources that will be used in the first few minutes need to be packed into the APK, while the rest of the content can be downloaded in the background after the game starts.
Developers are always creating new content for their games, so "change" is the only constant: different campaigns bring different launch screens and themes, keeping the game experience fresh for players.
Excelliance Tech’s LeBian (乐变) game assets streaming service helps game developers meet players’ needs by loading fresh resources dynamically while the game is loading or being played.
Meteor, Butterfly And a Sword (流星群侠传) by NetEase Games, Duoduo Auto Chess (多多自走棋) by Dragonest Game, Langrisser (梦幻模拟战) by ZlongGames, Junior Three Kingdom 2 (少年三国志 2) by Yoozoo Games - these games are created by different developers and have different look and feel, but one thing they have in common: they all use LeBian game streaming service to load resources.
The resource loading technology is so useful that Excelliance Tech is even using it in the LeBian SDK itself, bringing a better experience for developers. Dynamic resource loading makes the SDK much easier to use. By dynamically updating its internal resources when needed, the library doesn’t require developers to update the SDK for new resources.
Before Android 11 introduced the ResourcesLoader API, Excelliance Tech had to build their dynamic resource loading capability the hard way, using non-SDK interfaces.
When Excelliance was first building their product, Android did not offer public APIs for the dynamic resource loading use-case. The team did what they could, but ended up using non-SDK interfaces to add the external resources. While this met the technical need initially, the implementation was fragile - it depended on non-SDK interfaces, which don’t have the same compatibility guarantees as official SDK APIs and can change without notice.
As a result, Excelliance found that compatibility issues would surface unexpectedly as new versions of Android were released. These required additional testing and development to assure the stability of the product. Over many iterations, it took the Excelliance team six engineer-months and a lot of code to stabilize their solution, while knowing that it might break again in the next Android release. With Android tightening restrictions on non-SDK interfaces to achieve better stability and app compatibility, relying on those non-SDK interfaces became no longer an option.
As the Android team increased its focus on moving apps to public APIs, Excelliance saw an opportunity to migrate to a stronger foundation. They reached out to the Android team to give their feedback and highlighted their use case and need for public SDK APIs.
Over time, their collaboration led to the development of the ResourcesLoader public API that’s available for the first time in Android 11. Excelliance Tech has already moved to the new ResourcesLoader API and they’ve seen better productivity and product quality as a result. Excelliance believes the ResourcesLoader API provides advantages including the following:
String sdkroot = getApplicationInfo().dataDir + "/lebian"; ResourcesLoader rl = new ResourcesLoader(); rl.addProvider(ResourcesProvider.loadFromDirectory(sdkroot, null)); Resources res = getResources(); res.addLoaders(rl); final AssetManager assetManager = res.getAssets();
After moving to the new ResourcesLoader API, the essential code has just a few lines (down from hundreds of lines of code across a number of source files).
Excelliance Tech did a comparison test, loading 16,028 files (uncompressed 1.47GB, compressed 1.36GB) in 4 ways:
Resources are compressed in option 1, 2 and 3, and the average loading times are around 19 seconds. Option 4 loads uncompressed resources directly from a directory using ResourcesLoader, the average loading time is about 3 seconds - a 6x performance improvement!
Summarizing the overall impact of ResourcesLoader, Huang Gao, CEO & Product Lead at Excelliance Tech, said “The new ResourcesLoader API dramatically reduces development and maintenance costs and allows us to focus more on product and business innovation."
The Excelliance Tech team.
"On the Android platform, we've created some valuable products and services, which makes us want to invest more to create innovative products", Excelliance Tech stated, "We hope to have more opportunities to participate in the building of the Android ecosystem and contribute our efforts to make a better Android both for consumers and developers."
Excelliance Tech made an investment for the long-term compatibility of the LeBian SDK. Moving to the ResourcesLoader API has already yielded stability and performance benefits, reduced the complexity of their code, and reduced risks of future compatibility issues as Android rolls out new versions of the platform. The ResourcesLoader API is part of Android 11’s public APIs, benefitting the entire Android developer community.
Posted by Diana Wong, Product Manager, Android
This week in 11 Weeks of Android, we’re highlighting Android 11 Compatibility, a theme that’s important for all developers. For Android, the term app compatibility means that your app runs properly on a specific version of Android, typically the latest version.
You’ll hear more about these topics throughout the week. To get things started, read on to learn more about how we're making it easier to test and debug your app in Android 11.
Testing your app for a new Android release can be a challenging task, especially when your app might be affected by multiple platform changes. Many questions can come up:
targetSDKVersion,
We've gotten a lot of great feedback from our developer community about these and other questions. In Android 11, we've added new tools to the platform and new features to Android Studio that can make the testing process a little easier for you.
Like previous releases, Android 11 includes some changes in the Android platform that may impact your apps. Although these changes are critical to improve the platform, we try to minimize the immediate change to your apps by putting as many changes as possible behind the platform's latest targetSDKVersion. In Android 11, we've also added many of these platform changes to a new compatibility framework.
targetSDKVersion
When a change is part of the compatibility framework, you can access new developer tools that help you test and debug your app against that change.
For instance, changes that are part of the compatibility framework are toggleable, so you can force-enable or disable the changes individually, either from a device's developer options or using ADB (Android Debug Bridge). The Android platform automatically adapts its internal API logic, so you don't need to change your targetSDKVersion or recompile your app to perform basic testing. In addition, you can isolate individual changes from each other to lower the amount of time it takes to discover and debug issues in your app.
Before you start toggling changes on or off, you should read through the lists of behavior changes to determine which changes might affect your app. Changes that are part of the compatibility framework have a corresponding Change ID and Change Name listed before the description of the change.
Change ID
Change Name
Generally, we recommend that you start testing with behavior changes that affect all apps because those changes can potentially affect your app regardless of targetSDKVersion. However, let's take a look at a change that is gated by targetSDKVersion so that you can see how to test against these changes without recompiling your app with a different target SDK.
Take a look at the change to background location access. This change affects apps that request all-the-time access to background location. If your app is affected by this change, it might be a great candidate to start testing with. The change's name is BACKGROUND_RATIONALE_CHANGE_ID and the change's ID is 147316723. You'll use this information to enable this change before you test your app against it.
BACKGROUND_RATIONALE_CHANGE_ID
147316723
After deciding which change you want to test against, you can toggle that change on or off using the developer options. To get to the developer options, open your device's Settings app and navigate to System > Advanced > Developer options > App Compatibility Changes.
Toggleable platform changes in the developer options with the background location access change enabled
In this case, the BACKGROUND_RATIONALE_CHANGE_ID is the only change that is enabled to minimize scope of possible causes for any issues that your app might encounter.
You can also use logcat or ADB to identify which changes are enabled and use ADB to toggle changes on or off. Note that you can only toggle changes when using a debuggable app.
After enabling a change, you can test and debug your app using your typical testing workflows. If you encounter issues, check your logs to help determine the cause of the problem. If it's not clear whether the problem is caused by the platform change that's enabled, try disabling that change and then retest that area of your app.
Check out this week's video on testing platform changes in Android 11 to see another example and read the documentation on developer.android.com.
In addition to manual testing on the new platform, we’ve also made it easier to use Android Studio to run automated tests on the latest OS.
Starting in Android Studio 4.2, instrumentation tests can now be run across multiple physical or virtual devices in parallel. When running tests, there’s now the option to select Multiple Devices in the target device dropdown menu.
This feature is designed to help you catch issues as early as possible in your development cycle and allow you to compare differences between different builds of Android. The results of these tests can be investigated using a new Test Matrix under View > Tool Windows > Run.
The new Test Matrix lets you filter your test results by status, device, and API level.
Check out this week's video on testing app compatibility with Android Studio and read the documentation on developer.android.com.
We encourage you to try out these new tools and send us feedback about how they're working for you. We hope these tools help make it easier for you to test your app for Android 11.
Also, the Android engineering team will host a Reddit AMA on r/androiddev thursday, July 9 at 12:00PM PST, to answer your technical questions about Android 11. See this post for details and to submit your questions.
This blogpost is a collaboration between Google and Viber. Authored by Kseniia Shumelchyk from Google and Anton Novikov, Sergey Kozlov from Viber.
As a messaging app, Viber needs to store, process and share a significant amount of data. Viber aims to give its users an easy, fast, reliable and secure communication platform by providing an intuitive interface and operating with files in a privacy-preserving way. We believe the modern scoped storage paradigm provides this foundation for app developers and users.
Scoped storage was introduced in Android 10 with further improvements in Android 11 to provide better protection to app and user data on a platform level. Due to Viber's complexity, the team opted to incrementally implement the changes that were required to comply with scoped storage.
In this article, we’ll share how Viber handled the migration to scoped storage, focusing on what they did to optimize working with media files and other data in the app.
Android’s storage model has evolved to adapt to changing privacy considerations, leading to the changes in the storage system APIs. Let’s take a look at key platform changes that affected the legacy Viber implementation.
Scoped storage changes the way that apps store and access files on a device's external storage. Viber needed to evaluate the differences between the existing app's storage model and updated platform guidelines, followed by gradual application changes to work with files in scoped storage. Therefore Viber invoked the requestLegacyExternalStorage flag to temporarily opt-out of scoped storage on Android 10 until the app was fully compatible.
In order to adjust their app experience to scoped storage, Viber now contributes public media files to well-defined media collections using the MediaStore API. This way, the files are accessible in a device gallery, and can be read by other apps with the storage permission. Private media files are stored in the app-specific directory on external storage and are accessed via the internal ContentProvider.
The other notable update is related to changes in the storage permissions model: Apps in scoped storage have unrestricted access to their app-specific directories on external storage and can contribute to well-defined media collections without requesting a runtime permission. This change will help Viber provide more granular control to their users:
“This addition supports our efforts to provide our users with the best security and privacy solutions we can provide supported by the Android OS, users will benefit from this added security later without needing to opt-in. We also added a new ‘Save to gallery’ option allowing users to choose to make their photos readable by other apps or not. Because chats may contain private images or videos, it’s important to give users the ability to hide these files from the gallery. This change gives users additional control over the content included in their Viber messages.“ said Anton Novikov and Sergey Kozlov from Viber.
Previously, Viber created and consumed files in a custom top level directory and depended on file path access. With scoped storage, saving app files to a top level directory became an anti-pattern, so Viber has followed best practices to update their implementation to store media files from the chats only in locations that are accessible in scoped storage.
However, to reduce the complexity of migration, Viber decided to keep their own top level directory for Android 10 and below, storing only the media files that are not exposed to the device’s Gallery app, while for Android 11 and above this directory is used in read-only mode to provide backward compatibility.
Another use case that Viber has been refining is sharing files in the chats. The updated storage runtime permission gives read access only to the images, videos and audio files that are available through MediaProvider. Starting from Android 11, the only way for Viber to access non-media files created by other apps is by using the Storage Access Framework document picker, which they had already utilized in a different part of their app.
In the scoped storage environment, app-specific directories on external storage are becoming private from other apps. This change has helped Viber leverage its use of external storage for storing private user files:
”We find change to app-specific directories to be useful, because it will help to ensure that personal chats are protected and backed with platform security.” said Anton Novikov from Viber. Learn more about how to access app-specific files.
Because Viber targets a large audience running on Android 4.2 and above, they introduced an abstraction layer that aids them in managing storage access efficiently across all supported Android versions and with their use cases in mind.
Previously, Viber heavily used File API to access files, including files in legacy storage locations. Further, they stored absolute file paths for entries in the local database to keep the user's conversation history.
To standardize access to this conversation history and thus ensure that users don’t lose access to their files, Viber replaced absolute file paths with content URIs. In the new implementation, the app is accessing files only via content providers:
By using a consistent ContentProvider layer, the ContentResolver gives the app a unified interface to access the file content.
This approach has also helped Viber optimize the network layer and define a universal Loader abstraction to upload/fetch and to read/store different types of media files like voice messages, chat images and stickers.
Android 11 further enhances scoped storage, which provides better protection of app and user data and makes the transition easier for developers. It’s amazing to see many apps like Viber are migrating to take advantage of scoped storage since Android 10.
We hope Viber’s story is useful and will inspire you to modernize your Android apps as well. Learn more about Android storage use cases and best practices.
Posted by Platform Hardening Team
In Android 11 we continue to increase the security of the Android platform. We have moved to safer default settings, migrated to a hardened memory allocator, and expanded the use of compiler mitigations that defend against classes of vulnerabilities and frustrate exploitation techniques.
We’ve enabled forms of automatic memory initialization in both Android 11’s userspace and the Linux kernel. Uninitialized memory bugs occur in C/C++ when memory is used without having first been initialized to a known safe value. These types of bugs can be confusing, and even the term “uninitialized” is misleading. Uninitialized may seem to imply that a variable has a random value. In reality it isn’t random. It has whatever value was previously placed there. This value may be predictable or even attacker controlled. Unfortunately this behavior can result in a serious vulnerability such as information disclosure bugs like ASLR bypasses, or control flow hijacking via a stack or heap spray. Another possible side effect of using uninitialized values is advanced compiler optimizations may transform the code unpredictably, as this is considered undefined behavior by the relevant C standards.
In practice, uses of uninitialized memory are difficult to detect. Such errors may sit in the codebase unnoticed for years if the memory happens to be initialized with some "safe" value most of the time. When uninitialized memory results in a bug, it is often challenging to identify the source of the error, particularly if it is rarely triggered.Eliminating an entire class of such bugs is a lot more effective than hunting them down individually. Automatic stack variable initialization relies on a feature in the Clang compiler which allows choosing initializing local variables with either zeros or a pattern.Initializing to zero provides safer defaults for strings, pointers, indexes, and sizes. The downsides of zero init are less-safe defaults for return values, and exposing fewer bugs where the underlying code relies on zero initialization. Pattern initialization tends to expose more bugs and is generally safer for return values and less safe for strings, pointers, indexes, and sizes.
Automatic stack variable initialization is enabled throughout the entire Android userspace. During the development of Android 11, we initially selected pattern in order to uncover bugs relying on zero init and then moved to zero-init after a few months for increased safety. Platform OS developers can build with `AUTO_PATTERN_INITIALIZE=true m` if they want help uncovering bugs relying on zero init.
`AUTO_PATTERN_INITIALIZE=true m`
Automatic stack and heap initialization were recently merged in the upstream Linux kernel. We have made these features available on earlier versions of Android’s kernel including 4.14, 4.19, and 5.4. These features enforce initialization of local variables and heap allocations with known values that cannot be controlled by attackers and are useless when leaked. Both features result in a performance overhead, but also prevent undefined behavior improving both stability and security.
For kernel stack initialization we adopted the CONFIG_INIT_STACK_ALL from upstream Linux. It currently relies on Clang pattern initialization for stack variables, although this is subject to change in the future.
CONFIG_INIT_STACK_ALL
Heap initialization is controlled by two boot-time flags, init_on_alloc and init_on_free, with the former wiping freshly allocated heap objects with zeroes (think s/kmalloc/kzalloc in the whole kernel) and the latter doing the same before the objects are freed (this helps to reduce the lifetime of security-sensitive data). init_on_alloc is a lot more cache-friendly and has smaller performance impact (within 2%), therefore it has been chosen to protect Android kernels.
s/kmalloc/kzalloc
init_on_alloc
In Android 11, Scudo replaces jemalloc as the default native allocator for Android. Scudo is a hardened memory allocator designed to help detect and mitigate memory corruption bugs in the heap, such as:
Scudo does not fully prevent exploitation but it does add a number of sanity checks which are effective at strengthening the heap against some memory corruption bugs.
It also proactively organizes the heap in a way that makes exploitation of memory corruption more difficult, by reducing the predictability of the allocation patterns, and separating allocations by sizes.
In our internal testing, Scudo has already proven its worth by surfacing security and stability bugs that were previously undetected.
Android 11 introduces GWP-ASan, an in-production heap memory safety bug detection tool that's integrated directly into the native allocator Scudo. GWP-ASan probabilistically detects and provides actionable reports for heap memory safety bugs when they occur, works on 32-bit and 64-bit processes, and is enabled by default for system processes and system apps.
GWP-ASan is also available for developer applications via a one line opt-in in an app's AndroidManifest.xml, with no complicated build support or recompilation of prebuilt libraries necessary.
Continuing work on adopting the Arm Memory Tagging Extension (MTE) in Android, Android 11 includes support for kernel HWASAN, also known as Software Tag-Based KASAN. Userspace HWASAN is supported since Android 10.
KernelAddressSANitizer (KASAN) is a dynamic memory error detector designed to find out-of-bound and use-after-free bugs in the Linux kernel. Its Software Tag-Based mode is a software implementation of the memory tagging concept for the kernel. Software Tag-Based KASAN is available in 4.14, 4.19 and 5.4 Android kernels, and can be enabled with the CONFIG_KASAN_SW_TAGS kernel configuration option. Currently Tag-Based KASAN only supports tagging of slab memory; support for other types of memory (such as stack and globals) will be added in the future.
Compared to Generic KASAN, Tag-Based KASAN has significantly lower memory requirements (see this kernel commit for details), which makes it usable on dog food testing devices. Another use case for Software Tag-Based KASAN is checking the existing kernel code for compatibility with memory tagging. As Tag-Based KASAN is based on similar concepts as the future in-kernel MTE support, making sure that kernel code works with Tag-Based KASAN will ease in-kernel MTE integration in the future.
We’ve continued to expand the compiler mitigations that have been rolled out in prior releases as well. This includes adding both integer and bounds sanitizers to some core libraries that were lacking them. For example, the libminikin fonts library and the libui rendering library are now bounds sanitized. We’ve hardened the NFC stack by implementing both integer overflow sanitizer and bounds sanitizer in those components.
In addition to the hard mitigations like sanitizers, we also continue to expand our use of CFI as an exploit mitigation. CFI has been enabled in Android’s networking daemon, DNS resolver, and more of our core javascript libraries like libv8 and the PacProcessor.
Thank you to Jeff Vander Stoep, Alexander Potapenko, Stephen Hines, Andrey Konovalov, Mitch Phillips, Ivan Lozano, Kostya Kortchinsky, Christopher Ferris, Cindy Zhou, Evgenii Stepanov, Kevin Deus, Peter Collingbourne, Elliott Hughes, Kees Cook and Ken Chen for their contributions to this post.
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