Since KernelSU Manager can now be built for 32-bit, theres this problematic
setup where userspace is 32-bit (armeabi-v7a) and kernel is 64bit (aarch64).
On 64-bit kernels with CONFIG_COMPAT=y, 32-bit userspace passes 32-bit pointers.
These values are interpreted as 64-bit pointers without proper casting and that
results in invalid or near-null memory access.
This patch adds proper compat-mode handling with the ff changes:
- introduce a dedicated struct (`sepol_compat_data`) using u32 fields
- use `compat_ptr()` to safely convert 32-bit user pointers to kernel pointers
- adding a runtime `ksu_is_compat` flag to dynamically select between struct layouts
This prevents a near-null pointer dereference when handling SELinux
policy updates from 32-bit ksud in a 64-bit kernel.
Truth table:
kernel 32 + ksud 32, struct is u32, no compat_ptr
kernel 64 + ksud 32, struct is u32, yes compat_ptr
kernel 64 + ksud 64, struct is u64, no compat_ptr
Preprocessor check
64BIT=y COMPAT=y: define both structs, select dynamically
64BIT=y COMPAT=n: struct u64
64BIT=n: struct u32
Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>
c64d196a10