net: call net.ResolveIPAddr with nul char causes a panic in the goroutine on Windows build

[saito-tom]

What did you do?

My product's server crashed and reproduced the problem from the panic log.
The reproduction program is below.
https://play.golang.org/p/1FdRbei_83s

The reproduction program does not work on Go Playground. Create a windows build and run it.

What did you expect to see?

I wanted to return an error if an invalid string is passed.

addr:  127.0.0.1
err: lookup localhost: no such host

What did you see instead?

Output of Windows build binary (GOOS=windows go run resolve_ip.go)

0032:fixme:process:SetProcessPriorityBoost (0xffffffffffffffff,1): stub
addr:  127.0.0.1
panic: syscall: string with NUL passed to StringToUTF16

goroutine 6 [running]:
syscall.StringToUTF16(...)
        /home/st/Downloads/go/src/syscall/syscall_windows.go:30
syscall.StringToUTF16Ptr(0x4f03b7, 0xa, 0x0)
        /home/st/Downloads/go/src/syscall/syscall_windows.go:65 +0x8b
net.(*Resolver).lookupIP.func1(0x0, 0x0, 0x0, 0x0, 0x0)
        /home/st/Downloads/go/src/net/lookup_windows.go:99 +0xf1
net.(*Resolver).lookupIP.func2(0xc000004100, 0xc00003c240)
        /home/st/Downloads/go/src/net/lookup_windows.go:129 +0x32
created by net.(*Resolver).lookupIP
        /home/st/Downloads/go/src/net/lookup_windows.go:128 +0xf8
exit status 2

Output of Linux build binary (go run resolve_ip.go)

addr:  127.0.0.1
err: lookup localhost: no such host

System details

go version go1.12.4 linux/amd64
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/st/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/st/go"
GOPROXY=""
GORACE=""
GOROOT="/home/st/Downloads/go"
GOTMPDIR=""
GOTOOLDIR="/home/st/Downloads/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
uname -sr: Linux 4.19.32-1-MANJARO
LSB Version:	n/a
Distributor ID:	ManjaroLinux
Description:	Manjaro Linux
Release:	18.0.4
Codename:	Illyria
/usr/lib/libc.so.6: GNU C Library (GNU libc) stable release version 2.28.
gdb --version: GNU gdb (GDB) 8.2.1

[saito-tom]

In lookupIP, it seems like it is not good to call Deprecated syscall.StringToUTF16Ptr which causes panic.

lookupIP:

go/src/net/lookup_windows.go

Line 99 in 68d4b12

e := syscall.GetAddrInfoW(syscall.StringToUTF16Ptr(name), nil, &hints, &result)

syscall.StringToUTF16Ptr:

go/src/syscall/syscall_windows.go

Lines 65 to 66 in 68d4b12

	// Deprecated: Use UTF16PtrFromString instead.
	func StringToUTF16Ptr(s string) *uint16 { return &StringToUTF16(s)[0] }

go/src/syscall/syscall_windows.go

Lines 27 to 33 in 68d4b12

	// Deprecated: Use UTF16FromString instead.
	func StringToUTF16(s string) []uint16 {
	a, err := UTF16FromString(s)
	if err != nil {
	panic("syscall: string with NUL passed to StringToUTF16")
	}
	return a

[julieqiu]

/cc @mikioh @bradfitz

[gopherbot]

Change https://golang.org/cl/173362 mentions this issue: net: don't crash on Windows when Lookup name has null byte in string

[gopherbot]

Change https://golang.org/cl/217729 mentions this issue: net: don't check LookupHost error in TestLookupNullByte