// SPDX-License-Identifier: GPL-2.0/* * Copyright (C) 2020 Collabora Ltd. */#include <linux/sched.h>#include <linux/prctl.h>#include <linux/syscall_user_dispatch.h>#include <linux/uaccess.h>#include <linux/signal.h>#include <linux/elf.h> #include <linux/sched/signal.h>#include <linux/sched/task_stack.h> #include <asm/syscall.h> #include "common.h" static void trigger_sigsys(struct pt_regs *regs){	struct kernel_siginfo info; 	clear_siginfo(&info);	info.si_signo = SIGSYS;	info.si_code = SYS_USER_DISPATCH;	info.si_call_addr = (void __user *)KSTK_EIP(current);	info.si_errno = 0;	info.si_arch = syscall_get_arch(current);	info.si_syscall = syscall_get_nr(current, regs); 	force_sig_info(&info);} bool syscall_user_dispatch(struct pt_regs *regs){	struct syscall_user_dispatch *sd = &current->syscall_dispatch;	char state; 	if (likely(instruction_pointer(regs) - sd->offset < sd->len))		return false; 	if (unlikely(arch_syscall_is_vdso_sigreturn(regs)))		return false; 	if (likely(sd->selector)) {		/*		 * access_ok() is performed once, at prctl time, when		 * the selector is loaded by userspace.		 */		if (unlikely(__get_user(state, sd->selector))) {			force_exit_sig(SIGSEGV);			return true;		} 		if (likely(state == SYSCALL_DISPATCH_FILTER_ALLOW))			return false; 		if (state != SYSCALL_DISPATCH_FILTER_BLOCK) {			force_exit_sig(SIGSYS);			return true;		}	} 	sd->on_dispatch = true;	syscall_rollback(current, regs);	trigger_sigsys(regs); 	return true;} int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,			      unsigned long len, char __user *selector){	switch (mode) {	case PR_SYS_DISPATCH_OFF:		if (offset || len || selector)			return -EINVAL;		break;	case PR_SYS_DISPATCH_ON:		/*		 * Validate the direct dispatcher region just for basic		 * sanity against overflow and a 0-sized dispatcher		 * region.  If the user is able to submit a syscall from		 * an address, that address is obviously valid.		 */		if (offset && offset + len <= offset)			return -EINVAL; 		if (selector && !access_ok(selector, sizeof(*selector)))			return -EFAULT; 		break;	default:		return -EINVAL;	} 	current->syscall_dispatch.selector = selector;	current->syscall_dispatch.offset = offset;	current->syscall_dispatch.len = len;	current->syscall_dispatch.on_dispatch = false; 	if (mode == PR_SYS_DISPATCH_ON)		set_syscall_work(SYSCALL_USER_DISPATCH);	else		clear_syscall_work(SYSCALL_USER_DISPATCH); 	return 0;}