[Regression] Hard Crash/Reboot during high I/O (tar/apt) on OnePlus 13 - KSUN 32966

[UlasuNoka]

Device Information:

• Device: OnePlus 13 (CPH2653)
• ROM/Software Version: OOS 16.0.2.402(EX01) / Android 16
• SELinux Status: Permissive

Kernel Information:

• Base Linux Version: 6.6.89
• Problematic Build:
  AK3_OP13_OOS16_android15-6.6.89_KSUN_32966_SuSFS_v2.0.0 (v2.0.0-r7)
• Working Build:
  AK3_OP13_OOS16_android15-6.6.89_KSUN_32906_SuSFS_v2.0.0 (v2.0.0-r2)

Note: I have not tested the intermediate builds between v2.0.0-r2 and v2.0.0-r7 yet. I plan to test them to narrow down the regression and will report my findings in a follow-up comment.

Description:
I am experiencing a consistent hard crash (instant reboot) when performing intensive I/O operations inside a chroot environment (setup via manual mounting, not restricted by Linux Deploy). The issue specifically occurs when unpacking large archives or installing packages.
This appears to be a regression introduced between KSUN build 32906 and 32966, as the kernel version (6.6.89) and SuSFS version (v2.0.0) remain the same.

Steps to Reproduce:

1. Flash the problematic kernel (KSUN_32966).
2. Open a root terminal (via Termux tsu or ADB).
3. Attempt to unpack a large rootfs archive (e.g., Debian Sid rootfs ~200MB compressed):
   tar -xpf rootfs.tar.xz -C /data/chroot/target_dir/
   _Alternatively: _Run apt install for a large package inside the chroot.
4. Result: The device freezes for a few seconds and then hard reboots.

Troubleshooting & Regression Testing:

• I flashed the previous build (KSUN_32906) and the exact same operation completes successfully without any issues.
• I attempted to capture logs using console-ramoops and pmsg-ramoops after the reboot.
  • console-ramoops is empty.
  • pmsg-ramoops cuts off abruptly on standard Android logs (Wifi/Sync) with no indication of I/O errors or kernel panics, suggesting the crash is instantaneous and logs are not flushed to NVRAM in time.

Hypothesis:
Since the base kernel version is identical, the issue likely stems from changes in KernelSU Next hooks or specific scheduler/memory management patches applied in the 32966 build that conflict with heavy write operations on UFS.

[UlasuNoka]

Update on Bisection / Intermediate Testing:

I have tested all intermediate kernel releases between the working build (r2) and the latest broken build (r7) to pinpoint the exact start of the regression.

Here are the results:

• v2.0.0-r2 (KSUN 32906): ✅ Works (No crash)
• v2.0.0-r3 (KSUN 32940): ❌ Hard Crash
• v2.0.0-r4 (KSUN 32944): ❌ Hard Crash
• v2.0.0-r5 (KSUN 32953): ❌ Hard Crash
• v2.0.0-r6 (KSUN 32961): ❌ Hard Crash
• v2.0.0-r7 (KSUN 32966): ❌ Hard Crash (Original report)

Conclusion:
The regression was introduced immediately after build 32906. The first problematic build is 32940. This narrows down the problematic commit range significantly to the changes between these two versions.

Important Testing Note:
All tests listed above were performed with KernelSU modules disabled (clean environment) to strictly rule out any interference from third-party modules. The crash persists identically with or without modules enabled.

[UlasuNoka]

Update on the crashing issue:

We have narrowed down the cause in the main KernelSU-Next repo. The issue is not present on Google Pixel (confirmed by pershoot), but is 100% reproducible on OnePlus 13.

​I have performed detailed tests proving that Large Single Files (12GB) work perfectly, but High File Count archives cause an immediate crash. This points directly to a regression in how KSUN interacts with SUSFS hooks under high IOPS on this device.

​Please see our conversation here:
KernelSU-Next/KernelSU-Next#1106