In the current implementation, Magisk will either have to recreate
all early mount implementation (for legacy SAR and rootfs devices) or
delegate early mount to first stage init (for 2SI devices) to access
required partitions for loading sepolicy. It then has to recreate the
split sepolicy loading implementation in-house, apply patches, then
dump the compiled + patched policies into monolithic format somewhere.
Finally, it patches the original init to force it to load the sepolicy
file we just created.
With the increasing complexity involved in early mount and split
sepolicy (there is even APEX module involved in the future!),
it is about time to rethink Magisk's sepolicy strategy as rebuilding
init's functionality is not scalable and easy to maintain.
In this commit, instead of building sepolicy ourselves, we mock
selinuxfs with FIFO files connected to a pre-init daemon, waiting
for the actual init process to directly write the sepolicy file into
MagiskInit. We then patch the file and load it into the kernel. Some
FIFO tricks has to be used to hijack the original init process's
control flow and prevent race conditions, details are directly in the
comments in code.
At the moment, only system-as-root (read-only root) support is added.
Support for legacy rootfs devices will come with a follow up commit.
Design credit to @yujincheng08
Close#5146. Fix#5491, fix#3752
Previously, Magisk changes the mount point from /system to /system_root
by patching fstab to prevent the original init from changing root.
The reason why we want to prevent the original init from switching the
root directory is because it will then be read-only, making patching
and injecting magiskinit into the boot chain difficult.
This commit (ab)uses the fact that the /data folder will never be part
of early mount (because it is handled very late in the boot by vold),
so that we can use it as the mount point of tmpfs to store files.
Some advantages of this method:
- No need to switch root manually
- No need to modify fstab, which significantly improves compatibility
e.g. avoid hacks for weird devices like those using oplus.fstab,
and avoid hacking init to bypass fstab in device trees
- Supports skip_mount.cfg
- Support DSU
In the constructor of mmap_data, there are two possible values when fails: nullptr if fstat() fails, and MAP_FAILED if mmap() fails, but mmap_data treated MAP_FAILED as valid address and crashes.
Samsung FDE devices with the "persist.sys.zygote.early=true" property will cause Zygote to start before post-fs-data. According to Magisk's document, the post-fs-data phase should always happen before Zygote is started. Features assuming this behavior (like Zygisk and modules that need to control zygote) will not work. To avoid breaking existing modules, we simply invalidate this property to prevent this non-standard behavior from happening
Fix#5299, fix#5328, fix#5308
Co-authored-by: LoveSy <shana@zju.edu.cn>
* Further fix `oplus.fstab` support
In some oneplus devices, `oplus.fstab` does exists but `init` never
loaded it and those entries in `oplus.fstab` are written directly to
`fstab.qcom`. Previous implementation will introduce duplicate entries
to `fstab.qcom` and brick the device. This commit filters those entries
from `oplus.fstab` that are already in `fstab.qcom` and further filters
duplicated entries in `oplus.fstab` (keep only the last entry).
Fix#5016
* Fix UB
Since we moved entry, we need to explicitly copy its member.
For c++23 we can use `auto{}`.
- Use ftruncate64 instead of ftruncate to workaround seccomp
- Cast uint32_t to off64_t before making it negative
Note: Using ftruncate with a modern NDK libc should actually be
fine as the syscall wrapper in bionic will use ftruncate64 internally.
However, since we are using the libc.a from r10e built for Gingerbread,
seccomp wasn't a thing back then, and also the ftruncate64 symbol is
missing; we have to create our own wrapper and call it instead on
32-bit ABIs.
Props to @jnotuo for discovering the overflow bug and seccomp issue
Fix#3703, close#4915
`operator==` of string_view will create a tmp `string_view`.
It's an UB if the `const char *` is a nullptr.
`fdt_get_name` however will return a nullptr.
Samsung Galaxy A21S and Galaxy M12, probably others, are hdr_v2 boot.img with 2SI judging by the ramdisk contents, but the dtb contains an extra cmdline with skip_initramfs present, even though this shouldn't exist on 2SI and the kernel apparently doesn't even contain a skip_initramfs function
I can't find examples of other devices where skip_initramfs is present in the dtb other than these so patch it out like we do the kernel
Co-authored-by: topjohnwu <topjohnwu@gmail.com>
Custom ROM bring-ups of legacy Sony devices contain the following:
/init (symlink to /bin/init_sony)
/init.real (the "real" Android init)
/bin/init_sony (this was /sbin/init_sony on Android <11)
Kernel loads the ramdisk and starts /init -> /bin/init_sony
/bin/init_sony does low-level device setup (see: https://github.com/LineageOS/android_device_sony_common/blob/lineage-18.1/init/init_main.cpp)
/bin/init_sony unlinks /init and renames /init.real to /init
/bin/init_sony starts /init
Since init_sony needs to run first magiskinit needs to replace init.real instead, so add workarounds based on detection of init.real to boot patcher and uninstaller
Thanks @115ek and @bleckdeth
Fixes#3636
Co-authored-by: topjohnwu <topjohnwu@gmail.com>
Fix topjohnwu#4810
> [ 2.927463] [1: init: 1] magiskinit: Replace [/system/etc/selinux/plat_sepolicy.cil] -> [xxx]
[ 2.936801] [1: init: 1] magiskinit: write failed with 14: Bad address
Since topjohnwu#4596, magisk fails to patch `/init`, xwrite() fails with EFAULT, break the original `/init` file and make the device unbootable. Reverting this commit for legacy rootfs devices fixes the problem. I think this is a Samsung kernel magic since currently I can't reproduce this on other devices or find something special in the log currently we have.
- The lambda here infers its return type as `std::string`,
and since `info` is `const`, the labmda copies `info.name`
and returns a `std::string&&`. After captured by the
`std::string_view`, the `std::string&&` return value
deconstructs and makes `std::string_view` refers to a
dangling pointer.
libselinux.so will be unmounted when magiskd starts. If magiskd restarts (like it died before boot completed), the files we want to unmount is the original files because the modified files is unmounted in previous start, which will causes many crashes due to missing libselinux.so.
- In `unmap_all`, replace readable pages atomically with mmap + mremap
- Create new function `remap_all` to replace pages with equivalent
anonymous copies to prevent simple maps name scanning
* This seems to be a logic that has been abandoned for a
long time. Now we automatically choose which partition
to store sepolicy.rule. Furthermore, touching /persist is
what we should avoid doing whenever possible.
Fix#4204
`_root` is uninitialized for non-root nodes. And it will cause `module_node::mount` fail because it uses `root()`. Once the bug is triggered, signal 11 is received but Magisk catch all signals and therefore stuck forever.
* Support deodexed ROM: This should not be done and dexpreopt is mandatory since P
Xposed: Xposed handles them just fine, at least in the latest version 89.3
suMiscL6: For whatever audio mods, a leftover of phh time
Liveboot and suBackL6: Was for CF.lumen and LiveBoot, not needed now
* Also cleanup binder sepolicies since we allow all binder transactions.
faccessat() should return 0 when success, but it returns random number with errno == 0 in x86 platform.
It’s a side effect of commit bf80b08b5febd3f311108ff1c6e6a6bf2d1113b7 when magisk binaries ‘corretly’ linked with library of API16 .. lol
Co-authored-by: John Wu <topjohnwu@gmail.com>
