diff options
Diffstat (limited to 'kernel/entry')
| -rw-r--r-- | kernel/entry/Makefile | 2 | ||||
| -rw-r--r-- | kernel/entry/common.h | 7 | ||||
| -rw-r--r-- | kernel/entry/syscall_user_dispatch.c | 104 |
3 files changed, 112 insertions, 1 deletions
diff --git a/kernel/entry/Makefile b/kernel/entry/Makefile index 34c8a3f1c735..095c775e001e 100644 --- a/kernel/entry/Makefile +++ b/kernel/entry/Makefile @@ -9,5 +9,5 @@ KCOV_INSTRUMENT := n CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong CFLAGS_common.o += -fno-stack-protector -obj-$(CONFIG_GENERIC_ENTRY) += common.o +obj-$(CONFIG_GENERIC_ENTRY) += common.o syscall_user_dispatch.o obj-$(CONFIG_KVM_XFER_TO_GUEST_WORK) += kvm.o diff --git a/kernel/entry/common.h b/kernel/entry/common.h new file mode 100644 index 000000000000..f6e6d02f07fe --- /dev/null +++ b/kernel/entry/common.h @@ -0,0 +1,7 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _COMMON_H +#define _COMMON_H + +bool syscall_user_dispatch(struct pt_regs *regs); + +#endif diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c new file mode 100644 index 000000000000..b0338a5625d9 --- /dev/null +++ b/kernel/entry/syscall_user_dispatch.c @@ -0,0 +1,104 @@ +// 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 = ¤t->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))) + do_exit(SIGSEGV); + + if (likely(state == PR_SYS_DISPATCH_OFF)) + return false; + + if (state != PR_SYS_DISPATCH_ON) + do_exit(SIGSYS); + } + + 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; +} |