kernel: expose allowlist workaround as Kconfig option

Useful for situations where the SU allowlist is not kept after a reboot.
As per upstream this is only used for < 4.10 and Huawei HiSilicon devices.
but theres user reports having issues even on 4.14/4.19 samsung kernels.
Expose this option so users affected can opt-in.

Discussion:
	tiann#1249
	tiann#1346

References:
	tiann@f57d351
	tiann@b61cb30

Credits to respective authors:
	rhjdvsgsgks
	ExtremeXT

Reviewed-by: Alex <a.mihail@pm.me>
Co-Authored-By: ExtremeXT <75576145+extremext@users.noreply.github.com>
Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/Kconfig

@@ -14,4 +14,12 @@ config KSU_DEBUG
 	help
 	  Enable KernelSU debug mode.
 
+config KSU_ALLOWLIST_WORKAROUND
+        bool "KernelSU Session Keyring Init workaround"
+        depends on KSU
+        default n
+        help
+          Enable session keyring init workaround for problematic devices.
+          Useful for situations where the SU allowlist is not kept after a reboot.
+
 endmenu

kernel/core_hook.c

@@ -606,7 +606,7 @@ static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 	return -ENOSYS;
 }
 // kernel 4.4 and 4.9
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 static int ksu_key_permission(key_ref_t key_ref, const struct cred *cred,
 			      unsigned perm)
 {
@@ -638,7 +638,7 @@ static struct security_hook_list ksu_hooks[] = {
 	LSM_HOOK_INIT(task_prctl, ksu_task_prctl),
 	LSM_HOOK_INIT(inode_rename, ksu_inode_rename),
 	LSM_HOOK_INIT(task_fix_setuid, ksu_task_fix_setuid),
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 	LSM_HOOK_INIT(key_permission, ksu_key_permission)
 #endif
 };

kernel/kernel_compat.c

@@ -9,7 +9,7 @@
 #include <linux/uaccess.h>
 #include "klog.h" // IWYU pragma: keep
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 #include "linux/key.h"
 #include "linux/errno.h"
 #include "linux/cred.h"
@@ -78,7 +78,7 @@ void ksu_android_ns_fs_check()
 
 struct file *ksu_filp_open_compat(const char *filename, int flags, umode_t mode)
 {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 	if (init_session_keyring != NULL && !current_cred()->session_keyring &&
 	    (current->flags & PF_WQ_WORKER)) {
 		pr_info("installing init session keyring for older kernel\n");

kernel/kernel_compat.h

@@ -10,7 +10,7 @@ extern long ksu_strncpy_from_user_nofault(char *dst,
 					  const void __user *unsafe_addr,
 					  long count);
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 extern struct key *init_session_keyring;
 #endif