syscall: unix Sendto panic if nil Sockaddr provided

[nathanaelle]

What version of Go are you using (go version)?

1.19.1

Does this issue reproduce with the latest release?

yes.

What operating system and processor architecture are you using (go env)?

ubuntu linux 22.04 on amd64

What did you do?

syscall.Sendto(socket, buffer, flag, nil)

What did you expect to see?

as specified in https://linux.die.net/man/2/sendto

send(sockfd, buf, len, flags);

is equivalent to

sendto(sockfd, buf, len, flags, NULL, 0); 

What did you see instead?

we can see in https://cs.opensource.google/go/go/+/refs/tags/go1.19.1:src/syscall/syscall_unix.go;l=445

func Sendto(fd int, p []byte, flags int, to Sockaddr) (err error) {
	ptr, n, err := to.sockaddr()
	if err != nil {
		return err
	}
	return sendto(fd, p, flags, ptr, n)
}

the nil situation for to is not tested, thus a panic() occurs.

Suggestion

is it possible to add a test to avoid a panic() when to is set to nil like in SendmsgN() ( see: https://cs.opensource.google/go/go/+/refs/tags/go1.19.1:src/syscall/syscall_unix.go;l=400 ) ?

this issue may also impact :
– SendtoInet4
– SendtoInet6
– SendmsgNInet4
– SendmsgNInet6

[tklauser]

I think it would make sense to add the check for syscall.Sendto. The other functions (SendtoInet4, SendtoInet6, SendmsgNInet4, SendmsgNInet6) are defined in internal/syscall/unix and are only used internally by Go. As far as I can see all call sites pass a non-nil Sockaddr, so I'm not sure we'd need the check there.

/cc @ianlancetaylor

[gopherbot]

Change https://go.dev/cl/433504 mentions this issue: syscall: check if dest_addr is nil to prevent panic from Sendto

[gopherbot]

Change https://go.dev/cl/434515 mentions this issue: unix: allow calling Sendto with nil Sockaddr

[gopherbot]

Change https://go.dev/cl/434535 mentions this issue: syscall: check if to is nil to prevent panic from WSASendto