tomoyo: revert CONFIG_SECURITY_TOMOYO_LKM support

This patch reverts two TOMOYO patches that were merged into Linus' tree
during the v6.12 merge window:

8b985bb ("tomoyo: allow building as a loadable LSM module")
268225a ("tomoyo: preparation step for building as a loadable LSM module")

Together these two patches introduced the CONFIG_SECURITY_TOMOYO_LKM
Kconfig build option which enabled a TOMOYO specific dynamic LSM loading
mechanism (see the original commits for more details).  Unfortunately,
this approach was widely rejected by the LSM community as well as some
members of the general kernel community.  Objections included concerns
over setting a bad precedent regarding individual LSMs managing their
LSM callback registrations as well as general kernel symbol exporting
practices.  With little to no support for the CONFIG_SECURITY_TOMOYO_LKM
approach outside of Tetsuo, and multiple objections, we need to revert
these changes.

Link: https://lore.kernel.org/all/[email protected]
Link: https://lore.kernel.org/all/CAHC9VhR=QjdoHG3wJgHFJkKYBg7vkQH2MpffgVzQ0tAByo_wRg@mail.gmail.com
Acked-by: John Johansen <[email protected]>
Signed-off-by: Paul Moore <[email protected]>

Author: pcmoore

security/tomoyo/Kconfig

@@ -13,21 +13,6 @@ config SECURITY_TOMOYO
 	  found at <https://tomoyo.sourceforge.net/>.
 	  If you are unsure how to answer this question, answer N.
 
-config SECURITY_TOMOYO_LKM
-	bool "Cut out most of TOMOYO's code to a loadable kernel module"
-	default n
-	depends on SECURITY_TOMOYO
-	depends on MODULES
-	help
-	  Say Y here if you want to include TOMOYO without bloating
-	  vmlinux file. If you say Y, most of TOMOYO code is cut out to
-	  a loadable kernel module named tomoyo.ko . This option will be
-	  useful for kernels built by Linux distributors where TOMOYO is
-	  included but TOMOYO is not enabled by default. Please be sure
-	  to explicitly load tomoyo.ko if you want to activate TOMOYO
-	  without calling userspace policy loader, for tomoyo.ko is
-	  loaded immediately before calling userspace policy loader.
-
 config SECURITY_TOMOYO_MAX_ACCEPT_ENTRY
 	int "Default maximal count for learning mode"
 	default 2048

security/tomoyo/Makefile

@@ -1,11 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-tomoyo-objs := audit.o common.o condition.o domain.o environ.o file.o gc.o group.o memory.o mount.o network.o proxy.o realpath.o securityfs_if.o util.o
-obj-y += init.o load_policy.o
-ifdef CONFIG_SECURITY_TOMOYO_LKM
-obj-m += tomoyo.o
-else
-obj-y += tomoyo.o
-endif
+obj-y = audit.o common.o condition.o domain.o environ.o file.o gc.o group.o load_policy.o memory.o mount.o network.o realpath.o securityfs_if.o tomoyo.o util.o
 
 targets += builtin-policy.h
 

security/tomoyo/common.c

@@ -998,13 +998,8 @@ static bool tomoyo_select_domain(struct tomoyo_io_buffer *head,
 			p = find_task_by_pid_ns(pid, &init_pid_ns);
 		else
 			p = find_task_by_vpid(pid);
-		if (p) {
+		if (p)
 			domain = tomoyo_task(p)->domain_info;
-#ifdef CONFIG_SECURITY_TOMOYO_LKM
-			if (!domain)
-				domain = &tomoyo_kernel_domain;
-#endif
-		}
 		rcu_read_unlock();
 	} else if (!strncmp(data, "domain=", 7)) {
 		if (tomoyo_domain_def(data + 7))
@@ -1715,13 +1710,8 @@ static void tomoyo_read_pid(struct tomoyo_io_buffer *head)
 		p = find_task_by_pid_ns(pid, &init_pid_ns);
 	else
 		p = find_task_by_vpid(pid);
-	if (p) {
+	if (p)
 		domain = tomoyo_task(p)->domain_info;
-#ifdef CONFIG_SECURITY_TOMOYO_LKM
-		if (!domain)
-			domain = &tomoyo_kernel_domain;
-#endif
-	}
 	rcu_read_unlock();
 	if (!domain)
 		return;

security/tomoyo/common.h

@@ -978,7 +978,6 @@ int tomoyo_get_mode(const struct tomoyo_policy_namespace *ns, const u8 profile,
 int tomoyo_init_request_info(struct tomoyo_request_info *r,
 			     struct tomoyo_domain_info *domain,
 			     const u8 index);
-int __init tomoyo_interface_init(void);
 int tomoyo_mkdev_perm(const u8 operation, const struct path *path,
 		      const unsigned int mode, unsigned int dev);
 int tomoyo_mount_permission(const char *dev_name, const struct path *path,
@@ -1215,14 +1214,10 @@ static inline void tomoyo_put_group(struct tomoyo_group *group)
  *
  * Returns pointer to "struct tomoyo_task" for specified thread.
  */
-#ifdef CONFIG_SECURITY_TOMOYO_LKM
-extern struct tomoyo_task *tomoyo_task(struct task_struct *task);
-#else
 static inline struct tomoyo_task *tomoyo_task(struct task_struct *task)
 {
 	return task->security + tomoyo_blob_sizes.lbs_task;
 }
-#endif
 
 /**
  * tomoyo_same_name_union - Check for duplicated "struct tomoyo_name_union" entry.
@@ -1289,71 +1284,4 @@ static inline struct tomoyo_policy_namespace *tomoyo_current_namespace(void)
 		pos =  srcu_dereference((head)->next, &tomoyo_ss);	\
 	for ( ; pos != (head); pos = srcu_dereference(pos->next, &tomoyo_ss))
 
-#ifdef CONFIG_SECURITY_TOMOYO_LKM
-
-#define LSM_HOOK(RET, DEFAULT, NAME, ...) typedef RET (NAME##_t)(__VA_ARGS__);
-#include <linux/lsm_hook_defs.h>
-#undef LSM_HOOK
-
-struct tomoyo_hooks {
-	cred_prepare_t *cred_prepare;
-	bprm_committed_creds_t *bprm_committed_creds;
-	task_alloc_t *task_alloc;
-	task_free_t *task_free;
-	bprm_check_security_t *bprm_check_security;
-	file_fcntl_t *file_fcntl;
-	file_open_t *file_open;
-	file_truncate_t *file_truncate;
-	path_truncate_t *path_truncate;
-	path_unlink_t *path_unlink;
-	path_mkdir_t *path_mkdir;
-	path_rmdir_t *path_rmdir;
-	path_symlink_t *path_symlink;
-	path_mknod_t *path_mknod;
-	path_link_t *path_link;
-	path_rename_t *path_rename;
-	inode_getattr_t *inode_getattr;
-	file_ioctl_t *file_ioctl;
-	file_ioctl_compat_t *file_ioctl_compat;
-	path_chmod_t *path_chmod;
-	path_chown_t *path_chown;
-	path_chroot_t *path_chroot;
-	sb_mount_t *sb_mount;
-	sb_umount_t *sb_umount;
-	sb_pivotroot_t *sb_pivotroot;
-	socket_bind_t *socket_bind;
-	socket_connect_t *socket_connect;
-	socket_listen_t *socket_listen;
-	socket_sendmsg_t *socket_sendmsg;
-};
-
-extern void tomoyo_register_hooks(const struct tomoyo_hooks *tomoyo_hooks);
-
-struct tomoyo_operations {
-	void (*check_profile)(void);
-	int enabled;
-};
-
-extern struct tomoyo_operations tomoyo_ops;
-
-/*
- * Temporary hack: functions needed by tomoyo.ko . This will be removed
- * after all functions are marked as EXPORT_STMBOL_GPL().
- */
-struct tomoyo_tmp_exports {
-	struct task_struct * (*find_task_by_vpid)(pid_t nr);
-	struct task_struct * (*find_task_by_pid_ns)(pid_t nr, struct pid_namespace *ns);
-	void (*put_filesystem)(struct file_system_type *fs);
-	struct file * (*get_mm_exe_file)(struct mm_struct *mm);
-	char * (*d_absolute_path)(const struct path *path, char *buf, int buflen);
-};
-extern const struct tomoyo_tmp_exports tomoyo_tmp_exports;
-#define find_task_by_vpid tomoyo_tmp_exports.find_task_by_vpid
-#define find_task_by_pid_ns tomoyo_tmp_exports.find_task_by_pid_ns
-#define put_filesystem tomoyo_tmp_exports.put_filesystem
-#define get_mm_exe_file tomoyo_tmp_exports.get_mm_exe_file
-#define d_absolute_path tomoyo_tmp_exports.d_absolute_path
-
-#endif /* defined(CONFIG_SECURITY_TOMOYO_LKM) */
-
 #endif /* !defined(_SECURITY_TOMOYO_COMMON_H) */

security/tomoyo/gc.c

@@ -9,9 +9,6 @@
 #include <linux/kthread.h>
 #include <linux/slab.h>
 
-/* Lock for GC. */
-DEFINE_SRCU(tomoyo_ss);
-
 /**
  * tomoyo_memory_free - Free memory for elements.
  *