With Android 13, Google has prevented the Pixel 6, 6 Pro and 6a from reinstalling Android 12 to address a security issue. Addressing that vulnerability can lead to another problem and Google has released instructions to avoid bricking your device if you’ve flashed Android 13.
What’s different with the Android 13 update for Pixel 6
A security issue exists with the previous bootloader on the Pixel 6 series and Android 13 prevents the vulnerable version of Android 12 from being reinstalled.
Even after flashing an Android 13 factory image – which is different from sideloading an OTA image – on the Pixel 6 series and updating successfully, an Android 12 build will remain on your phone. This is due to Android’s A/B (seamless) system updates, which are intended to provide redundancy:
A/B system updates use two sets of partitions called slots (normally slot A and slot B). The system runs from the current slot while the partitions in the unused slot are inaccessible to the running system during normal operation. This approach makes updates error-proof by keeping the unused slot as a fallback: if an error occurs during or immediately after an update, the system can revert to the old slot and a working system remains.
As such, the “inactive slot contains an older bootloader whose anti-rollback version has not been increased.” That mismatch can cause problems if you flash your device and something goes wrong with the installation. By design, Android will try to boot from the inactive slot, but that goes against the vulnerability protection. Considering it’s Android 12 (and the older bootloader), your phone won’t turn on.
If your Android 13 . flashed
Google issued instructions Thursday afternoon to prevent that particular issue from happening. It involves flashing the inactive slot from Android 12 to Android 13. The easiest option is to sideload an OTA image – which updates the inactive slot – but there are steps for using factory images as well.
This process is mainly aimed at those (ie tinkerers) who are going to reflash their devices with a factory or custom image (built on AOSP).
Meanwhile, in the coming days, Google will update the Android Flash Tool — which flashes the active slot, like fastboot — with a prompt to flash the inactive slot with the Android 13 bootloader.
If you used the Android 13 OTA
Those who sideload an Android 13 OTA image (a process without device/data wipe) or accepted the OTA on the device (Google’s recommended installation method) and not going to flash (again, other than sideloading) their phones “don’t need to take any action for now.”
|Slot A||Castle B|
|Android 12 (July Sec Patch)||Android 12 (June)|
|Android 12 (July)||Android 13 (August)|
|android the 13th of September)||Android 13 (August)|
The company also tells us that there is a very small chance of encountering the problem for the vast majority of users with locked bootloaders. The next OTA (presumably the September security patch) or sideload will update the inactive slot.
Kyle Bradshaw and Dylan Roussel contributed to this article.
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