Dear all, I remember having read here or on the internet that flashing an already updated Fairphone could result in bricking the device if the Android security update is too recent.
I’m not sure to remember correctly and I don’t want to take any risk: I have two FP4 both with Android 13. One has Build dated june 26 2024 and Android security update dated july 5 2024. The second unit has Build dated march 13 2024 and Security update march 5 2024.
They should both be flashable but could anybody please confirm and remind me what’s the exact condition to avoid when flashing an used FP4 ?
Caution: The FP4 comes with an anti-rollback feature. Google Android anti-roll back feature is supposedly a way to ensure you are running the latest software version, including the latest security patches.
If you try installing a version of /e/OS based on a security patch that is older than the one on your device, you will brick your device. Click on Details below for detailed information
Details
To check the security patch level on your phone with a locked bootloader, prior to installing /e/OS, open your phone Settings » About Phone » Android Version » Android Security Patch Level.Then compare it against the level of the security patch on the /e/OS build as visible in the Downloads for FP4 section below.
The following values control whether anti-rollback features are triggered on FP4:
Rollback protection errors trigger if you install an update whose version number is LESS than the rollback index’s value stored on device.
The value of rollback index is UPDATED to match ro.build.version.security_patch’s value of the currently installed version, but only if the bootloader is LOCKED.
The value of rollback index is NOT dependent on the currently installed ANDROID VERSION.
The value of rollback index can NEVER be DOWNGRADED.
Rollback protection errors are FATAL when the bootloader is LOCKED.
Rollback protection errors are IGNORED when the bootloader is UNLOCKED.
Here are some examples to help you understand how anti-rollback features work:
Example 1
Your FP4 with Google Android has a Security Patch Level saying June 5, 2022
The /e/OS build available says: /e/OS build : R official (Security patch: 2022-05-05)
In this example, the /e/OS build has an older Security Patch level than the origin, so the anti-roll back protection will trigger, and you will brick your phone
Example 2
Your FP4 with Google Android has a Security Patch Level saying June 5, 2022.
The /e/OS build available says: /e/OS build : R official (Security patch: 2022-06-05)
In this example, the /e/OS build has the same Security Patch level than the origin, so the anti-roll back protection will pass, and you will be able to install /e/OS with no issues.
Example 3
Your FP4 runs Google Android -R while /e/OS is now available based on AOSP -S.
Your FP4 with Google Android has a Security Patch Level saying 2022-10-03 or October 3rd, 2022.
The /e/OS build available says: /e/OS build : S official (Security patch: 2022-06-05)
In this example, the /e/OS build has an older Security Patch level than the origin, so the anti-roll back protection will trigger, even if the /e/OS version runs on a more recent version of AOSP. In this example, you will brick your phone.
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So the two things to compare are
Current locked Fairphone Android SPL of the installed OS.
The Android SPL of your intended /e/OS build from Release notes – and search Security fixes, to find the entry for the install candidate, as today I find
If you try installing a version of /e/OS based on a security patch that is older than the one on your device, you will brick your device, if / when you try to lock it again.
