#include <linux/kernel.h>#include <linux/syscalls.h>#include <linux/fdtable.h>#include <linux/string.h>#include <linux/random.h>#include <linux/module.h>#include <linux/ptrace.h>#include <linux/init.h>#include <linux/errno.h>#include <linux/cache.h>#include <linux/bug.h>#include <linux/err.h>#include <linux/kcmp.h>#include <linux/capability.h>#include <linux/list.h>#include <linux/eventpoll.h>#include <linux/file.h> #include <asm/unistd.h> /* * We don't expose the real in-memory order of objects for security reasons. * But still the comparison results should be suitable for sorting. So we * obfuscate kernel pointers values and compare the production instead. * * The obfuscation is done in two steps. First we xor the kernel pointer with * a random value, which puts pointer into a new position in a reordered space. * Secondly we multiply the xor production with a large odd random number to * permute its bits even more (the odd multiplier guarantees that the product * is unique ever after the high bits are truncated, since any odd number is * relative prime to 2^n). * * Note also that the obfuscation itself is invisible to userspace and if needed * it can be changed to an alternate scheme. */static unsigned long cookies[KCMP_TYPES][2] __read_mostly; static long kptr_obfuscate(long v, int type){	return (v ^ cookies[type][0]) * cookies[type][1];} /* * 0 - equal, i.e. v1 = v2 * 1 - less than, i.e. v1 < v2 * 2 - greater than, i.e. v1 > v2 * 3 - not equal but ordering unavailable (reserved for future) */static int kcmp_ptr(void *v1, void *v2, enum kcmp_type type){	long t1, t2; 	t1 = kptr_obfuscate((long)v1, type);	t2 = kptr_obfuscate((long)v2, type); 	return (t1 < t2) | ((t1 > t2) << 1);} /* The caller must have pinned the task */static struct file *get_file_raw_ptr(struct task_struct *task, unsigned int idx){	struct file *file = NULL; 	task_lock(task);	rcu_read_lock(); 	if (task->files)		file = fcheck_files(task->files, idx); 	rcu_read_unlock();	task_unlock(task); 	return file;} static void kcmp_unlock(struct mutex *m1, struct mutex *m2){	if (likely(m2 != m1))		mutex_unlock(m2);	mutex_unlock(m1);} static int kcmp_lock(struct mutex *m1, struct mutex *m2){	int err; 	if (m2 > m1)		swap(m1, m2); 	err = mutex_lock_killable(m1);	if (!err && likely(m1 != m2)) {		err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);		if (err)			mutex_unlock(m1);	} 	return err;} #ifdef CONFIG_EPOLLstatic int kcmp_epoll_target(struct task_struct *task1,			     struct task_struct *task2,			     unsigned long idx1,			     struct kcmp_epoll_slot __user *uslot){	struct file *filp, *filp_epoll, *filp_tgt;	struct kcmp_epoll_slot slot;	struct files_struct *files; 	if (copy_from_user(&slot, uslot, sizeof(slot)))		return -EFAULT; 	filp = get_file_raw_ptr(task1, idx1);	if (!filp)		return -EBADF; 	files = get_files_struct(task2);	if (!files)		return -EBADF; 	spin_lock(&files->file_lock);	filp_epoll = fcheck_files(files, slot.efd);	if (filp_epoll)		get_file(filp_epoll);	else		filp_tgt = ERR_PTR(-EBADF);	spin_unlock(&files->file_lock);	put_files_struct(files); 	if (filp_epoll) {		filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);		fput(filp_epoll);	} else 	if (IS_ERR(filp_tgt))		return PTR_ERR(filp_tgt); 	return kcmp_ptr(filp, filp_tgt, KCMP_FILE);}#elsestatic int kcmp_epoll_target(struct task_struct *task1,			     struct task_struct *task2,			     unsigned long idx1,			     struct kcmp_epoll_slot __user *uslot){	return -EOPNOTSUPP;}#endif SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,		unsigned long, idx1, unsigned long, idx2){	struct task_struct *task1, *task2;	int ret; 	rcu_read_lock(); 	/*	 * Tasks are looked up in caller's PID namespace only.	 */	task1 = find_task_by_vpid(pid1);	task2 = find_task_by_vpid(pid2);	if (!task1 || !task2)		goto err_no_task; 	get_task_struct(task1);	get_task_struct(task2); 	rcu_read_unlock(); 	/*	 * One should have enough rights to inspect task details.	 */	ret = kcmp_lock(&task1->signal->cred_guard_mutex,			&task2->signal->cred_guard_mutex);	if (ret)		goto err;	if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||	    !ptrace_may_access(task2, PTRACE_MODE_READ_REALCREDS)) {		ret = -EPERM;		goto err_unlock;	} 	switch (type) {	case KCMP_FILE: {		struct file *filp1, *filp2; 		filp1 = get_file_raw_ptr(task1, idx1);		filp2 = get_file_raw_ptr(task2, idx2); 		if (filp1 && filp2)			ret = kcmp_ptr(filp1, filp2, KCMP_FILE);		else			ret = -EBADF;		break;	}	case KCMP_VM:		ret = kcmp_ptr(task1->mm, task2->mm, KCMP_VM);		break;	case KCMP_FILES:		ret = kcmp_ptr(task1->files, task2->files, KCMP_FILES);		break;	case KCMP_FS:		ret = kcmp_ptr(task1->fs, task2->fs, KCMP_FS);		break;	case KCMP_SIGHAND:		ret = kcmp_ptr(task1->sighand, task2->sighand, KCMP_SIGHAND);		break;	case KCMP_IO:		ret = kcmp_ptr(task1->io_context, task2->io_context, KCMP_IO);		break;	case KCMP_SYSVSEM:#ifdef CONFIG_SYSVIPC		ret = kcmp_ptr(task1->sysvsem.undo_list,			       task2->sysvsem.undo_list,			       KCMP_SYSVSEM);#else		ret = -EOPNOTSUPP;#endif		break;	case KCMP_EPOLL_TFD:		ret = kcmp_epoll_target(task1, task2, idx1, (void *)idx2);		break;	default:		ret = -EINVAL;		break;	} err_unlock:	kcmp_unlock(&task1->signal->cred_guard_mutex,		    &task2->signal->cred_guard_mutex);err:	put_task_struct(task1);	put_task_struct(task2); 	return ret; err_no_task:	rcu_read_unlock();	return -ESRCH;} static __init int kcmp_cookies_init(void){	int i; 	get_random_bytes(cookies, sizeof(cookies)); 	for (i = 0; i < KCMP_TYPES; i++)		cookies[i][1] |= (~(~0UL >>  1) | 1); 	return 0;}arch_initcall(kcmp_cookies_init);