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// Copyright 2015 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package host
import (
"bytes"
"fmt"
"io/ioutil"
"runtime"
"strconv"
"strings"
"sync"
"syscall"
"github.com/google/syzkaller/pkg/osutil"
"github.com/google/syzkaller/prog"
)
func isSupported(c *prog.Syscall, sandbox string) (bool, string) {
// There are 3 possible strategies for detecting supported syscalls:
// 1. Executes all syscalls with presumably invalid arguments and check for ENOprog.
// But not all syscalls are safe to execute. For example, pause will hang,
// while setpgrp will push the process into own process group.
// 2. Check presence of /sys/kernel/debug/tracing/events/syscalls/sys_enter_* files.
// This requires root and CONFIG_FTRACE_SYSCALLS. Also it lies for some syscalls.
// For example, on x86_64 it says that sendfile is not present (only sendfile64).
// 3. Check sys_syscallname in /proc/kallsyms.
// Requires CONFIG_KALLSYMS. Seems to be the most reliable. That's what we use here.
kallsymsOnce.Do(func() {
kallsyms, _ = ioutil.ReadFile("/proc/kallsyms")
})
if strings.HasPrefix(c.CallName, "syz_") {
return isSupportedSyzkall(sandbox, c)
}
if strings.HasPrefix(c.Name, "socket$") {
return isSupportedSocket(c)
}
if strings.HasPrefix(c.Name, "openat$") {
return isSupportedOpenAt(c)
}
if len(kallsyms) == 0 {
return true, ""
}
name := c.CallName
if newname := kallsymsMap[name]; newname != "" {
name = newname
}
if !bytes.Contains(kallsyms, []byte(" T sys_"+name+"\n")) &&
!bytes.Contains(kallsyms, []byte(" T ksys_"+name+"\n")) &&
!bytes.Contains(kallsyms, []byte(" T __ia32_sys_"+name+"\n")) &&
!bytes.Contains(kallsyms, []byte(" T __x64_sys_"+name+"\n")) {
return false, fmt.Sprintf("sys_%v is not present in /proc/kallsyms", name)
}
return true, ""
}
// Some syscall names diverge in __NR_* consts and kallsyms.
// umount2 is renamed to umount in arch/x86/entry/syscalls/syscall_64.tbl.
// Where umount is renamed to oldumount is unclear.
var (
kallsyms []byte
kallsymsOnce sync.Once
kallsymsMap = map[string]string{
"umount": "oldumount",
"umount2": "umount",
}
)
func isSupportedSyzkall(sandbox string, c *prog.Syscall) (bool, string) {
switch c.CallName {
case "syz_open_dev":
if _, ok := c.Args[0].(*prog.ConstType); ok {
// This is for syz_open_dev$char/block.
// They are currently commented out, but in case one enables them.
return true, ""
}
fname, ok := extractStringConst(c.Args[0])
if !ok {
panic("first open arg is not a pointer to string const")
}
var check func(dev string) bool
check = func(dev string) bool {
if !strings.Contains(dev, "#") {
return osutil.IsExist(dev)
}
for i := 0; i < 10; i++ {
if check(strings.Replace(dev, "#", strconv.Itoa(i), 1)) {
return true
}
}
return false
}
if !check(fname) {
return false, fmt.Sprintf("file %v does not exist", fname)
}
return onlySandboxNoneOrNamespace(sandbox)
case "syz_open_procfs":
return true, ""
case "syz_open_pts":
return true, ""
case "syz_fuse_mount":
if !osutil.IsExist("/dev/fuse") {
return false, "/dev/fuse does not exist"
}
return onlySandboxNoneOrNamespace(sandbox)
case "syz_fuseblk_mount":
if !osutil.IsExist("/dev/fuse") {
return false, "/dev/fuse does not exist"
}
return onlySandboxNoneOrNamespace(sandbox)
case "syz_emit_ethernet", "syz_extract_tcp_res":
fd, err := syscall.Open("/dev/net/tun", syscall.O_RDWR, 0)
if err != nil {
return false, fmt.Sprintf("open(/dev/net/tun) failed: %v", err)
}
syscall.Close(fd)
return true, ""
case "syz_kvm_setup_cpu":
switch c.Name {
case "syz_kvm_setup_cpu$x86":
if runtime.GOARCH == "amd64" || runtime.GOARCH == "386" {
return true, ""
}
case "syz_kvm_setup_cpu$arm64":
if runtime.GOARCH == "arm64" {
return true, ""
}
}
return false, "unsupported arch"
case "syz_init_net_socket":
// Unfortunately this only works with sandbox none at the moment.
// The problem is that setns of a network namespace requires CAP_SYS_ADMIN
// in the target namespace, and we've lost all privs in the init namespace
// during creation of a user namespace.
if ok, reason := onlySandboxNone(sandbox); !ok {
return false, reason
}
return isSupportedSocket(c)
case "syz_genetlink_get_family_id":
fd, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_RAW, syscall.NETLINK_GENERIC)
if fd == -1 {
return false, fmt.Sprintf("socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC) failed: %v", err)
}
syscall.Close(fd)
return true, ""
case "syz_mount_image":
return onlySandboxNone(sandbox)
case "syz_read_part_table":
return onlySandboxNone(sandbox)
}
panic("unknown syzkall: " + c.Name)
}
func onlySandboxNone(sandbox string) (bool, string) {
if syscall.Getuid() != 0 || sandbox != "none" {
return false, "only supported under root with sandbox=none"
}
return true, ""
}
func onlySandboxNoneOrNamespace(sandbox string) (bool, string) {
if syscall.Getuid() != 0 || sandbox == "setuid" {
return false, "only supported under root with sandbox=none/namespace"
}
return true, ""
}
func isSupportedSocket(c *prog.Syscall) (bool, string) {
af, ok := c.Args[0].(*prog.ConstType)
if !ok {
panic("socket family is not const")
}
fd, err := syscall.Socket(int(af.Val), 0, 0)
if fd != -1 {
syscall.Close(fd)
}
if err == syscall.ENOSYS {
return false, "socket syscall returns ENOSYS"
}
if err == syscall.EAFNOSUPPORT {
return false, "socket family is not supported (EAFNOSUPPORT)"
}
return true, ""
}
func isSupportedOpenAt(c *prog.Syscall) (bool, string) {
fname, ok := extractStringConst(c.Args[1])
if !ok || len(fname) == 0 || fname[0] != '/' {
return true, ""
}
fd, err := syscall.Open(fname, syscall.O_RDONLY, 0)
if fd != -1 {
syscall.Close(fd)
}
if err != nil {
return false, fmt.Sprintf("open(%v) failed: %v", fname, err)
}
return true, ""
}
func extractStringConst(typ prog.Type) (string, bool) {
ptr, ok := typ.(*prog.PtrType)
if !ok {
panic("first open arg is not a pointer to string const")
}
str, ok := ptr.Type.(*prog.BufferType)
if !ok || str.Kind != prog.BufferString || len(str.Values) != 1 {
return "", false
}
v := str.Values[0]
v = v[:len(v)-1] // string terminating \x00
return v, true
}
func EnableFaultInjection() error {
if err := osutil.WriteFile("/sys/kernel/debug/failslab/ignore-gfp-wait", []byte("N")); err != nil {
return fmt.Errorf("failed to write /failslab/ignore-gfp-wait: %v", err)
}
if err := osutil.WriteFile("/sys/kernel/debug/fail_futex/ignore-private", []byte("N")); err != nil {
return fmt.Errorf("failed to write /fail_futex/ignore-private: %v", err)
}
if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem", []byte("N")); err != nil {
return fmt.Errorf("failed to write /fail_page_alloc/ignore-gfp-highmem: %v", err)
}
if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait", []byte("N")); err != nil {
return fmt.Errorf("failed to write /fail_page_alloc/ignore-gfp-wait: %v", err)
}
if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/min-order", []byte("0")); err != nil {
return fmt.Errorf("failed to write /fail_page_alloc/min-order: %v", err)
}
return nil
}
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