"Preflash Validation Failed" when Flashing Magisk-Patched Boot Image (v28+)

[saitarunsareddy]

Device: Moto G64 5G India
Android version: 14
Magisk version name: 218327f
Magisk version code: 28101

When attempting to flash a Magisk-patched boot image created using Magisk v28 or v28.1 on a Moto G64 5G device, the process fails with the error:

Preflash validation failed

However, when the boot image is patched using Magisk v27, the flashing process completes successfully without errors. This suggests a compatibility issue introduced in Magisk v28+ that prevents the bootloader from accepting the patched boot image.

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Device Information:

• Device Model: Moto G64 5G India
• Android Version: 14
• Bootloader Status: Unlocked
• Firmware Version: CANCUNF_G_SYS_U1TDS34.100_46_7_2 (Latest)
• Magisk Version: v28.0, v28.1 (fails), v27.0 (works)
• Fastboot Version: fastboot version 35.0.2-12147458

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Steps to Reproduce:

1. Extract the stock boot.img from the firmware.

2. Patch the boot.img using Magisk v28.0 or v28.1.

3. Flash the patched boot image via fastboot:

   fastboot flash boot magisk_patched.img
   

4. Observe the error:

   Preflash validation failed
   

5. Repeat the same process using Magisk v27.0 to patch the boot.img.

6. Flashing succeeds without errors.

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Expected Behavior:

The Magisk-patched boot image created with v28+ should flash successfully, as it does with v27.

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Observed Behavior:

• Magisk v28+ patched boot image results in "Preflash validation failed."
• Magisk v27 patched boot image flashes successfully.

Attached Magisk patched images of v27, v28 and v28.1 uploaded in Google Drive and shared the link below:

Google Drive

Attached screenshots of fastboot error for 3 different boot images.

Thank you for your assistance in resolving this issue.

[Yorikiro]

Having a similar issue with poco F5 pro, no error message on fastboot, but cellphone won't boot

[DJLevel3]

Same issue on Moto G Stylus 5g 2024 (boston)

[John0n1]

It seems like a regression introduced in Magisk v28 related to boot image padding is causing the "Preflash validation failed" error on some devices.

The release notes for v28 mention a change in MagiskBoot: "Don't pad zeros if signed boot image is larger". It is highly likely that this change is the root cause of the problem. It's possible that some bootloaders are sensitive to the exact size and padding of the boot image, and the new padding behavior in v28 is not compatible with these bootloaders.

[A-Australian]

Maybe flash empty vb-meta?