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// Copyright 2017 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 linux
import (
"runtime"
"github.com/google/syzkaller/prog"
)
func initTarget(target *prog.Target) {
arch := &arch{
mmapSyscall: target.SyscallMap["mmap"],
clockGettimeSyscall: target.SyscallMap["clock_gettime"],
PROT_READ: target.ConstMap["PROT_READ"],
PROT_WRITE: target.ConstMap["PROT_WRITE"],
MAP_ANONYMOUS: target.ConstMap["MAP_ANONYMOUS"],
MAP_PRIVATE: target.ConstMap["MAP_PRIVATE"],
MAP_FIXED: target.ConstMap["MAP_FIXED"],
MREMAP_MAYMOVE: target.ConstMap["MREMAP_MAYMOVE"],
MREMAP_FIXED: target.ConstMap["MREMAP_FIXED"],
S_IFREG: target.ConstMap["S_IFREG"],
S_IFCHR: target.ConstMap["S_IFCHR"],
S_IFBLK: target.ConstMap["S_IFBLK"],
S_IFIFO: target.ConstMap["S_IFIFO"],
S_IFSOCK: target.ConstMap["S_IFSOCK"],
SYSLOG_ACTION_CONSOLE_OFF: target.ConstMap["SYSLOG_ACTION_CONSOLE_OFF"],
SYSLOG_ACTION_CONSOLE_ON: target.ConstMap["SYSLOG_ACTION_CONSOLE_ON"],
SYSLOG_ACTION_SIZE_UNREAD: target.ConstMap["SYSLOG_ACTION_SIZE_UNREAD"],
FIFREEZE: target.ConstMap["FIFREEZE"],
FITHAW: target.ConstMap["FITHAW"],
PTRACE_TRACEME: target.ConstMap["PTRACE_TRACEME"],
CLOCK_REALTIME: target.ConstMap["CLOCK_REALTIME"],
}
target.PageSize = pageSize
target.DataOffset = dataOffset
target.MmapSyscall = arch.mmapSyscall
target.MakeMmap = arch.makeMmap
target.AnalyzeMmap = arch.analyzeMmap
target.SanitizeCall = arch.sanitizeCall
target.SpecialStructs = map[string]func(g *prog.Gen, typ *prog.StructType, old *prog.GroupArg) (prog.Arg, []*prog.Call){
"timespec": arch.generateTimespec,
"timeval": arch.generateTimespec,
}
target.StringDictionary = stringDictionary
if target.Arch == runtime.GOARCH {
KCOV_INIT_TRACE = uintptr(target.ConstMap["KCOV_INIT_TRACE"])
KCOV_ENABLE = uintptr(target.ConstMap["KCOV_ENABLE"])
KCOV_TRACE_CMP = uintptr(target.ConstMap["KCOV_TRACE_CMP"])
}
}
const (
pageSize = 4 << 10
dataOffset = 512 << 20
invalidFD = ^uint64(0)
)
var (
// This should not be here, but for now we expose this for syz-fuzzer.
KCOV_INIT_TRACE uintptr
KCOV_ENABLE uintptr
KCOV_TRACE_CMP uintptr
stringDictionary = []string{"user", "keyring", "trusted", "system", "security", "selinux",
"posix_acl_access", "mime_type", "md5sum", "nodev", "self",
"bdev", "proc", "cgroup", "cpuset",
"lo", "eth0", "eth1", "em0", "em1", "wlan0", "wlan1", "ppp0", "ppp1",
"vboxnet0", "vboxnet1", "vmnet0", "vmnet1", "GPL"}
)
type arch struct {
mmapSyscall *prog.Syscall
clockGettimeSyscall *prog.Syscall
PROT_READ uint64
PROT_WRITE uint64
MAP_ANONYMOUS uint64
MAP_PRIVATE uint64
MAP_FIXED uint64
MREMAP_MAYMOVE uint64
MREMAP_FIXED uint64
S_IFREG uint64
S_IFCHR uint64
S_IFBLK uint64
S_IFIFO uint64
S_IFSOCK uint64
SYSLOG_ACTION_CONSOLE_OFF uint64
SYSLOG_ACTION_CONSOLE_ON uint64
SYSLOG_ACTION_SIZE_UNREAD uint64
FIFREEZE uint64
FITHAW uint64
PTRACE_TRACEME uint64
CLOCK_REALTIME uint64
}
// createMmapCall creates a "normal" mmap call that maps [start, start+npages) page range.
func (arch *arch) makeMmap(start, npages uint64) *prog.Call {
meta := arch.mmapSyscall
return &prog.Call{
Meta: meta,
Args: []prog.Arg{
prog.MakePointerArg(meta.Args[0], start, 0, npages, nil),
prog.MakeConstArg(meta.Args[1], npages*pageSize),
prog.MakeConstArg(meta.Args[2], arch.PROT_READ|arch.PROT_WRITE),
prog.MakeConstArg(meta.Args[3], arch.MAP_ANONYMOUS|arch.MAP_PRIVATE|arch.MAP_FIXED),
prog.MakeResultArg(meta.Args[4], nil, invalidFD),
prog.MakeConstArg(meta.Args[5], 0),
},
Ret: prog.MakeReturnArg(meta.Ret),
}
}
func (arch *arch) analyzeMmap(c *prog.Call) (start, npages uint64, mapped bool) {
switch c.Meta.Name {
case "mmap":
// Filter out only very wrong arguments.
npages = c.Args[1].(*prog.ConstArg).Val / pageSize
if npages == 0 {
return
}
flags := c.Args[3].(*prog.ConstArg).Val
fd := c.Args[4].(*prog.ResultArg).Val
if flags&arch.MAP_ANONYMOUS == 0 && fd == invalidFD {
return
}
start = c.Args[0].(*prog.PointerArg).PageIndex
mapped = true
return
case "munmap":
start = c.Args[0].(*prog.PointerArg).PageIndex
npages = c.Args[1].(*prog.ConstArg).Val / pageSize
mapped = false
return
case "mremap":
start = c.Args[4].(*prog.PointerArg).PageIndex
npages = c.Args[2].(*prog.ConstArg).Val / pageSize
mapped = true
return
default:
return
}
}
func (arch *arch) sanitizeCall(c *prog.Call) {
switch c.Meta.CallName {
case "mmap":
// Add MAP_FIXED flag, otherwise it produces non-deterministic results.
c.Args[3].(*prog.ConstArg).Val |= arch.MAP_FIXED
case "mremap":
// Add MREMAP_FIXED flag, otherwise it produces non-deterministic results.
flags := c.Args[3].(*prog.ConstArg)
if flags.Val&arch.MREMAP_MAYMOVE != 0 {
flags.Val |= arch.MREMAP_FIXED
}
case "mknod", "mknodat":
pos := 1
if c.Meta.CallName == "mknodat" {
pos = 2
}
mode := c.Args[pos].(*prog.ConstArg)
dev := c.Args[pos+1].(*prog.ConstArg)
// Char and block devices read/write io ports, kernel memory and do other nasty things.
// TODO: not required if executor drops privileges.
switch mode.Val & (arch.S_IFREG | arch.S_IFCHR | arch.S_IFBLK | arch.S_IFIFO | arch.S_IFSOCK) {
case arch.S_IFREG, arch.S_IFIFO, arch.S_IFSOCK:
case arch.S_IFBLK:
// TODO(dvyukov): mknod dev argument is uint32,
// but prog arguments contain not-truncated uint64 values,
// so we can mistakenly assume that this is not loop, when it actually is.
// This is not very harmful, but need to verify other arguments in this function.
if dev.Val>>8 == 7 {
break // loop
}
mode.Val &^= arch.S_IFBLK
mode.Val |= arch.S_IFREG
case arch.S_IFCHR:
mode.Val &^= arch.S_IFCHR
mode.Val |= arch.S_IFREG
}
case "syslog":
cmd := c.Args[0].(*prog.ConstArg)
// These disable console output, but we need it.
if cmd.Val == arch.SYSLOG_ACTION_CONSOLE_OFF || cmd.Val == arch.SYSLOG_ACTION_CONSOLE_ON {
cmd.Val = arch.SYSLOG_ACTION_SIZE_UNREAD
}
case "ioctl":
cmd := c.Args[1].(*prog.ConstArg)
// Freeze kills machine. Though, it is an interesting functions,
// so we need to test it somehow.
// TODO: not required if executor drops privileges.
if uint64(uint32(cmd.Val)) == arch.FIFREEZE {
cmd.Val = arch.FITHAW
}
case "ptrace":
req := c.Args[0].(*prog.ConstArg)
// PTRACE_TRACEME leads to unkillable processes, see:
// https://groups.google.com/forum/#!topic/syzkaller/uGzwvhlCXAw
if req.Val == arch.PTRACE_TRACEME {
req.Val = ^uint64(0)
}
case "exit", "exit_group":
code := c.Args[0].(*prog.ConstArg)
// These codes are reserved by executor.
if code.Val%128 == 67 || code.Val%128 == 68 {
code.Val = 1
}
}
}
func (arch *arch) generateTimespec(g *prog.Gen, typ *prog.StructType, old *prog.GroupArg) (arg prog.Arg, calls []*prog.Call) {
// We need to generate timespec/timeval that are either
// (1) definitely in the past, or
// (2) definitely in unreachable fututre, or
// (3) few ms ahead of now.
// Note: timespec/timeval can be absolute or relative to now.
// Note: executor has blocking syscall timeout of 20ms,
// so we generate both 10ms and 30ms.
usec := typ.Name() == "timeval"
switch {
case g.NOutOf(1, 4):
// Now for relative, past for absolute.
arg = prog.MakeGroupArg(typ, []prog.Arg{
prog.MakeResultArg(typ.Fields[0], nil, 0),
prog.MakeResultArg(typ.Fields[1], nil, 0),
})
case g.NOutOf(1, 3):
// Few ms ahead for relative, past for absolute
nsec := uint64(10 * 1e6)
if g.NOutOf(1, 2) {
nsec = 30 * 1e6
}
if usec {
nsec /= 1e3
}
arg = prog.MakeGroupArg(typ, []prog.Arg{
prog.MakeResultArg(typ.Fields[0], nil, 0),
prog.MakeResultArg(typ.Fields[1], nil, nsec),
})
case g.NOutOf(1, 2):
// Unreachable fututre for both relative and absolute
arg = prog.MakeGroupArg(typ, []prog.Arg{
prog.MakeResultArg(typ.Fields[0], nil, 2e9),
prog.MakeResultArg(typ.Fields[1], nil, 0),
})
default:
// Few ms ahead for absolute.
meta := arch.clockGettimeSyscall
ptrArgType := meta.Args[1].(*prog.PtrType)
argType := ptrArgType.Type.(*prog.StructType)
tp := prog.MakeGroupArg(argType, []prog.Arg{
prog.MakeResultArg(argType.Fields[0], nil, 0),
prog.MakeResultArg(argType.Fields[1], nil, 0),
})
var tpaddr prog.Arg
tpaddr, calls = g.Alloc(ptrArgType, tp)
gettime := &prog.Call{
Meta: meta,
Args: []prog.Arg{
prog.MakeConstArg(meta.Args[0], arch.CLOCK_REALTIME),
tpaddr,
},
Ret: prog.MakeReturnArg(meta.Ret),
}
calls = append(calls, gettime)
sec := prog.MakeResultArg(typ.Fields[0], tp.(*prog.GroupArg).Inner[0], 0)
nsec := prog.MakeResultArg(typ.Fields[1], tp.(*prog.GroupArg).Inner[1], 0)
msec := uint64(10)
if g.NOutOf(1, 2) {
msec = 30
}
if usec {
nsec.(*prog.ResultArg).OpDiv = 1e3
nsec.(*prog.ResultArg).OpAdd = msec * 1e3
} else {
nsec.(*prog.ResultArg).OpAdd = msec * 1e6
}
arg = prog.MakeGroupArg(typ, []prog.Arg{sec, nsec})
}
return
}
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