[Bug Fix Guide] Partial Solutions for Issues with Older Kernels where KernelSU Doesn't Work and Module Functionality Fails

[Coconutat]

Partial Solutions for Issues with Older Kernels where KernelSU Doesn't Work and Module Functionality Fails

1. Preface:

This guide is dedicated to those who are still using older devices without custom ROMs.

The targeted kernel versions and Android versions (I don't have devices with even older versions, so compatibility is not guaranteed for versions other than those listed below):

Kernel versions: 4.4, 4.9.
Android versions: Android 8 (O), Android 9 (P).

Prerequisite Reading: Manually Integrate KernelSU

Note 1: If KPROBES is not functioning properly, you should abandon KPROBES instead of persistently trying to make it work. Code is static; humans are dynamic.

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Note 2:

For manual integration, you should disable KPROBES, as it can lead to issues such as reboots and crashes. To disable it, find the following lines in your defconfig file:

CONFIG_KPROBES=y
CONFIG_HAVE_KPROBES=y
CONFIG_KPROBE_EVENTS=y

Change them to:

# CONFIG_KPROBES is not set
# CONFIG_HAVE_KPROBES is not set
# CONFIG_KPROBE_EVENTS is not set

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2. Fixes for Some Bugs:

Bug 1: SU Works, but Modules Don't

Solution: Modify hook.c

The code is located in:

security/selinux/hooks.c

Patch for modification: security: selinux: allow init exec (kernelsu:ksud) under nosuid

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Bug 2: KernelSU Works on Devices Below Android 10, but SU Authorization Doesn't Work Properly, and the Module Page Shows No Overlay_FS Support

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This bug has been fixed in v0.6.9.

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Obsolete Content:

Disclaimer: You should not consider the following content as a final solution because it is not secure and is self-deception.

Since KernelSU is not compatible with devices running Android 10 or earlier, it cannot handle init below Android 10 correctly. As a result, it gets intercepted by SELinux. However, at this point, you can't switch the SELinux status via adb commands, so the only option is to modify the code in selinxfs.c to forcibly set it to Permissive mode permanently. The downside of this is that it becomes highly detectable and severely compromises security.

The code is located in:

security/selinux/selinuxfs.c

Patch for modification: security:selinux:selinuxfs.c: Make SELinux Mode Always in permissive mode

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Bug 3:UMOUNT For Non GKI 4.4+ Kernels
Thanks, by @wxt1221 #1060

cherry-pick theses commits in ksu

• https://github.com/wxt1221/KernelSU/commit/ae8a14e708e2ee859912218d70623ee08a80b762
• https://github.com/wxt1221/KernelSU/commit/194e09fcf11a001dab285837620ce66351fb9cf2
• https://github.com/wxt1221/KernelSU/commit/5574642b20b0f7780fa9a2e3643eb8f99141bd68
• https://github.com/wxt1221/KernelSU/commit/fce6f6ed6ed649df51ab468c57b9ff698fcb2701

on kernel side do the following changes in fs/namespace.c
Bot-wxt1221/android_kernel_oneplus_sdm845@70ace81#diff-26b064824bfafef546f17235dc1f34dbea87ce6c27f9320b5d4427bfa4d2b0e9

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Good Tips:

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1. For Kernel 3.18 follow this guide by @ananjaser1211
2. Compile Kernel guide For Huawei EMUI 9 /9.1.0 User

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Other bugs are still being collected and investigated...

[anuragpindoriya]

Need help to fix this issue

#959

[Coconutat]

Did you enable CONFIG_KSU=y?I did't see it.

[Coconutat]

And disable KPROBES!!

[anuragpindoriya]

CONFIG KPROBES is not set
CONFIG_JUMP_LABEL is not set
CONFIG_UPROBES=y
ONFIG HAVE_64BIT_ALIGNED_ACCESS is not set
CONFIG HAVE_EFFICIENT UNALIGNED_ACCESS=y
CONFIG_HAVE_KPHIES=y
CONFIG_HAVE_KRETPROBES=Y
CONFIG HAVE_ARCH_TRACEHOOK=Y
CONFIG_HAVE_DMA_CONTIGUOUS=Y
CONFIG_GENERIC_SMP_IDLE_THREAD=y

Which one

[Coconutat]

CONFIG KPROBES is not set
CONFIG_JUMP_LABEL is not set
CONFIG_UPROBES=y
ONFIG HAVE_64BIT_ALIGNED_ACCESS is not set
CONFIG HAVE_EFFICIENT UNALIGNED_ACCESS=y
CONFIG_HAVE_KPHIES=y
CONFIG_HAVE_KRETPROBES=Y
CONFIG HAVE_ARCH_TRACEHOOK=Y
CONFIG_HAVE_DMA_CONTIGUOUS=Y
CONFIG_GENERIC_SMP_IDLE_THREAD=y

Which one

If you had read this post, you wouldn't have this question.

[rushiranpise]

For Kernel 3.18 follow this guide by @ananjaser1211
#539 (comment)

[testingweb624]

Hi, I am on lineage-20 , op6T device.

First I followed kprobe method , the su works but modules shows disabled button.

Second I followed manual one and its same. Su works but in modules section the enable/disable buttons are greyed out i.e disabled.

Any suggestion please.

Kernel version- 4.9.337
Device - oneplus 6T

[testingweb624]

Sorry please ignore this, I just missed the "bug 1" section. Following that one now.

[rushiranpise]

UMOUNT For Non GKI 4.4+ Kernels by @wxt1221 #1060

cherry-pick theses commits in ksu

1. https://github.com/wxt1221/KernelSU/commit/ae8a14e708e2ee859912218d70623ee08a80b762
2. https://github.com/wxt1221/KernelSU/commit/194e09fcf11a001dab285837620ce66351fb9cf2
3. https://github.com/wxt1221/KernelSU/commit/5574642b20b0f7780fa9a2e3643eb8f99141bd68
4. https://github.com/wxt1221/KernelSU/commit/fce6f6ed6ed649df51ab468c57b9ff698fcb2701

on kernel side do the following changes in fs/namespace.c
Bot-wxt1221/android_kernel_oneplus_sdm845@70ace81#diff-26b064824bfafef546f17235dc1f34dbea87ce6c27f9320b5d4427bfa4d2b0e9

add path_umount implementation
OnlyTomInSecond/android_kernel_xiaomi_sm8250@e9d65c4

[Ardjlon]

Is this supposed to work so that the modules are not detected?
Because I am doing test for an app, but it always detect modules.img (4.14)

[Bot-wxt1221]

That thy we should umount modules. It is for hiding modules

[Ardjlon]

The dmsg messages show that it dismounts correctly, but the app still detects the modules

[Bot-wxt1221]

That's a bug I think.

[backslashxx]

Is this supposed to work so that the modules are not detected? Because I am doing test for an app, but it always detect modules.img (4.14)

hit and miss and it depends on the module (if its modifying /system or /vendor partitions and the likes) then module needs to be mounted global, try using magic overlayfs.
actually kernelsu is looking at adding ksufs (seems a modification of overlayfs) for this reason exactly, I think.