Clean up kernel code (#2898)

1) Fix memory leak of callback head in allowlist.c
2) Remove duplicated logic and incorrect log in kernel_umount.c
3) Prevent sleep in kprobe context in ksud.c
4) Remove useless is_unsupported_uid, use euid for security enhance,
   add FIXME in setuid_hook.c
5) Remove useless fd argument for execve hook, fix incorrent pointer
   usage in syscall_hook_manager.c and sucompat.c
6) Use correct errno in supercalls.c

---------

Co-authored-by: Ylarod <me@ylarod.cn>

kernel/allowlist.c

@@ -402,6 +402,7 @@ close_file:
     filp_close(fp, 0);
 unlock:
     mutex_unlock(&allowlist_mutex);
+    kfree(_cb);
 }
 
 void persistent_allow_list()

kernel/kernel_umount.c

@@ -439,8 +439,6 @@ int ksu_handle_umount(uid_t old_uid, uid_t new_uid)
 
     if (!ksu_uid_should_umount(new_uid)) {
         return 0;
-    } else {
-        pr_info("uid: %d should not umount!\n", current_uid().val);
     }
 
     // check old process's selinux context, if it is not zygote, ignore it!

kernel/ksud.c

@@ -209,7 +209,6 @@ static int __maybe_unused count(struct user_arg_ptr argv, int max)
 
             if (fatal_signal_pending(current))
                 return -ERESTARTNOHAND;
-            cond_resched();
         }
     }
     return i;

kernel/setuid_hook.c

@@ -65,6 +65,10 @@
 
 #include "sulog.h"
 
+#define PER_USER_RANGE 100000
+#define FIRST_APPLICATION_UID 10000
+#define LAST_APPLICATION_UID 19999
+
 static bool ksu_enhanced_security_enabled = false;
 
 static int enhanced_security_feature_get(u64 *value)
@@ -119,19 +123,8 @@ static inline bool is_allow_su(void)
     return ksu_is_allow_uid_for_current(current_uid().val);
 }
 
-static inline bool is_unsupported_uid(uid_t uid)
+static inline bool is_appuid(uid_t uid)
 {
-#define LAST_APPLICATION_UID 19999
-    uid_t appid = uid % 100000;
-    return appid > LAST_APPLICATION_UID;
-}
-
-static bool is_appuid(uid_t uid)
-{
-#define PER_USER_RANGE 100000
-#define FIRST_APPLICATION_UID 10000
-#define LAST_APPLICATION_UID 19999
-
     uid_t appid = uid % PER_USER_RANGE;
     return appid >= FIRST_APPLICATION_UID && appid <= LAST_APPLICATION_UID;
 }
@@ -434,28 +427,28 @@ int ksu_handle_setresuid(uid_t ruid, uid_t euid, uid_t suid)
 {
     uid_t new_uid = ruid;
 	uid_t old_uid = current_uid().val;
-    pr_info("handle_setuid from %d to %d\n", old_uid, new_uid);
     
-    if (0 != old_uid) {
+    pr_info("handle_setresuid from %d to %d\n", old_uid, new_uid);
-        // old process is not root, ignore it.
+
-        if (ksu_enhanced_security_enabled) {
+    // if old process is root, ignore it.
-            // disallow any non-ksu domain escalation from non-root to root!
+    if (old_uid != 0 && ksu_enhanced_security_enabled) {
-            if (unlikely(new_uid) == 0) {
+        // disallow any non-ksu domain escalation from non-root to root!
-                if (!is_ksu_domain()) {
+        // euid is what we care about here as it controls permission
-                    pr_warn("find suspicious EoP: %d %s, from %d to %d\n", 
+        if (unlikely(euid == 0)) {
-                        current->pid, current->comm, old_uid, new_uid);
+            if (!is_ksu_domain()) {
-                    force_sig(SIGKILL);
+                pr_warn("find suspicious EoP: %d %s, from %d to %d\n", 
-                    return 0;
+                    current->pid, current->comm, old_uid, new_uid);
-                }
+                force_sig(SIGKILL);
+                return 0;
             }
-            // disallow appuid decrease to any other uid if it is allowed to su
+        }
-            if (is_appuid(old_uid)) {
+        // disallow appuid decrease to any other uid if it is not allowed to su
-                if (new_uid < old_uid && !ksu_is_allow_uid_for_current(old_uid)) {
+        if (is_appuid(old_uid)) {
-                    pr_warn("find suspicious EoP: %d %s, from %d to %d\n", 
+            if (euid < current_euid().val && !ksu_is_allow_uid_for_current(old_uid)) {
-                        current->pid, current->comm, old_uid, new_uid);
+                pr_warn("find suspicious EoP: %d %s, from %d to %d\n", 
-                    force_sig(SIGKILL);
+                    current->pid, current->comm, old_uid, new_uid);
-                    return 0;
+                force_sig(SIGKILL);
-                }
+                return 0;
             }
         }
         return 0;
@@ -465,14 +458,15 @@ int ksu_handle_setresuid(uid_t ruid, uid_t euid, uid_t suid)
         ksu_set_task_tracepoint_flag(current);
     }
 
-    if (!is_appuid(new_uid) || is_unsupported_uid(new_uid)) {
+    // FIXME: isolated process which directly forks from zygote is not handled
-        pr_info("handle setuid ignore non application or isolated uid: %d\n", new_uid);
+    if (!is_appuid(new_uid)) {
+        pr_info("handle setresuid ignore non application or isolated uid: %d\n", new_uid);
         ksu_clear_task_tracepoint_flag(current);
         return 0;
     }
 
     // if on private space, see if its possibly the manager
-    if (new_uid > 100000 && new_uid % 100000 == ksu_get_manager_uid()) {
+    if (new_uid > PER_USER_RANGE && new_uid % PER_USER_RANGE == ksu_get_manager_uid()) {
          ksu_set_manager_uid(new_uid);
     }
 

kernel/sucompat.c

@@ -63,8 +63,8 @@ bool ksu_sucompat_hook_state __read_mostly = true;
 
 static inline void __user *userspace_stack_buffer(const void *d, size_t len)
 {
-    /* To avoid having to mmap a page in userspace, just write below the stack
+    // To avoid having to mmap a page in userspace, just write below the stack
-   * pointer. */
+    // pointer.
     char __user *p = (void __user *)current_user_stack_pointer() - len;
 
     return copy_to_user(p, d, len) ? NULL : p;
@@ -190,7 +190,7 @@ int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags)
     return 0;
 }
 
-int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
+int ksu_handle_execve_sucompat(const char __user **filename_user,
                    void *__never_use_argv, void *__never_use_envp,
                    int *__never_use_flags)
 {
@@ -282,7 +282,7 @@ int __ksu_handle_devpts(struct inode *inode)
     return 0;
 }
 
-// sucompat: permited process can execute 'su' to gain root access.
+// sucompat: permitted process can execute 'su' to gain root access.
 void ksu_sucompat_init()
 {
     if (ksu_register_feature_handler(&su_compat_handler)) {

kernel/sucompat.h

@@ -11,7 +11,7 @@ void ksu_sucompat_exit(void);
 int ksu_handle_faccessat(int *dfd, const char __user **filename_user,
 			 int *mode, int *__unused_flags);
 int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
-int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
+int ksu_handle_execve_sucompat(const char __user **filename_user,
 			       void *__never_use_argv, void *__never_use_envp,
 			       int *__never_use_flags);
 

kernel/supercalls.c

@@ -360,7 +360,7 @@ static int do_set_feature(void __user *arg)
 
 static int do_get_wrapper_fd(void __user *arg) {
     if (!ksu_file_sid) {
-        return -1;
+        return -EINVAL;
     }
 
     struct ksu_get_wrapper_fd_cmd cmd;

kernel/syscall_hook_manager.c

@@ -217,7 +217,7 @@ static inline bool check_syscall_fastpath(int nr)
     }
 }
 
-int ksu_handle_init_mark_tracker(int *fd, const char __user **filename_user,
+int ksu_handle_init_mark_tracker(const char __user **filename_user,
                                void *__never_use_argv, void *__never_use_envp,
                                int *__never_use_flags)
 {
@@ -300,11 +300,9 @@ static void ksu_sys_enter_handler(void *data, struct pt_regs *regs, long id)
 				const char __user **filename_user =
 					(const char __user **)&PT_REGS_PARM1(regs);
 				if (current->pid == 1) {
-					ksu_handle_init_mark_tracker(AT_FDCWD, filename_user, 
+					ksu_handle_init_mark_tracker(filename_user, NULL, NULL, NULL);
-                        NULL, NULL, NULL);
 				} else {
-                    ksu_handle_execve_sucompat(AT_FDCWD, filename_user, NULL, 
+                    ksu_handle_execve_sucompat(filename_user, NULL, NULL, NULL);
-                        NULL, NULL);
                 }
 				return;
 			}