linux-kernel - Re: [PATCH v7 04/11] net/socket: Break down __sys

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Date:   Thu, 19 Oct 2023 12:12:03 -0700
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Breno Leitao <leitao@...ian.org>
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, io-uring@...r.kernel.org,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Alexander Mikhalitsyn <alexander@...alicyn.com>,
        David Howells <dhowells@...hat.com>, sdf@...gle.com,
        axboe@...nel.dk, asml.silence@...il.com,
        willemdebruijn.kernel@...il.com, kuba@...nel.org,
        pabeni@...hat.com, krisman@...e.de,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v7 04/11] net/socket: Break down __sys_getsockopt

On 10/16/23 6:47 AM, Breno Leitao wrote:
> diff --git a/net/socket.c b/net/socket.c
> index 0087f8c071e7..f4c156a1987e 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2350,6 +2350,42 @@ SYSCALL_DEFINE5(setsockopt, int, fd, int, level, int, optname,
>   INDIRECT_CALLABLE_DECLARE(bool tcp_bpf_bypass_getsockopt(int level,
>   							 int optname));
>   
> +int do_sock_getsockopt(struct socket *sock, bool compat, int level,
> +		       int optname, sockptr_t optval, sockptr_t optlen)
> +{
> +	int max_optlen __maybe_unused;
> +	const struct proto_ops *ops;
> +	int err;
> +
> +	err = security_socket_getsockopt(sock, level, optname);
> +	if (err)
> +		return err;
> +
> +	ops = READ_ONCE(sock->ops);
> +	if (level == SOL_SOCKET) {
> +		err = sk_getsockopt(sock->sk, level, optname, optval, optlen);
> +	} else if (unlikely(!ops->getsockopt)) {
> +		err = -EOPNOTSUPP;
> +	} else {
> +		if (WARN_ONCE(optval.is_kernel || optlen.is_kernel,
> +			      "Invalid argument type"))
> +			return -EOPNOTSUPP;
> +
> +		err = ops->getsockopt(sock, level, optname, optval.user,
> +				      optlen.user);
> +	}
> +
> +	if (!compat) {
> +		max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);

The max_optlen was done before the above sk_getsockopt. The bpf CI cannot catch 
it because it cannot apply patch 5 cleanly. I ran the following out of the 
linux-block tree:

$> ./test_progs -t sockopt_sk
test_sockopt_sk:PASS:join_cgroup /sockopt_sk 0 nsec
run_test:PASS:skel_load 0 nsec
run_test:PASS:setsockopt_link 0 nsec
run_test:PASS:getsockopt_link 0 nsec
(/data/users/kafai/fb-kernel/linux/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c:111: 
errno: Operation not permitted) Failed to call getsockopt, ret=-1
run_test:FAIL:getsetsockopt unexpected error: -1 (errno 1)
#217     sockopt_sk:FAIL


> +		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname,
> +						     optval, optlen, max_optlen,
> +						     err);
> +	}
> +
> +	return err;
> +}
> +EXPORT_SYMBOL(do_sock_getsockopt);
> +
>   /*
>    *	Get a socket option. Because we don't know the option lengths we have
>    *	to pass a user mode parameter for the protocols to sort out.
> @@ -2357,37 +2393,18 @@ INDIRECT_CALLABLE_DECLARE(bool tcp_bpf_bypass_getsockopt(int level,
>   int __sys_getsockopt(int fd, int level, int optname, char __user *optval,
>   		int __user *optlen)
>   {
> -	int max_optlen __maybe_unused;
> -	const struct proto_ops *ops;
>   	int err, fput_needed;
>   	struct socket *sock;
> +	bool compat;
>   
>   	sock = sockfd_lookup_light(fd, &err, &fput_needed);
>   	if (!sock)
>   		return err;
>   
> -	err = security_socket_getsockopt(sock, level, optname);
> -	if (err)
> -		goto out_put;
> -
> -	if (!in_compat_syscall())
> -		max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);

The old max_optlen was done here.

> +	compat = in_compat_syscall();
> +	err = do_sock_getsockopt(sock, compat, level, optname,
> +				 USER_SOCKPTR(optval), USER_SOCKPTR(optlen));
>   
> -	ops = READ_ONCE(sock->ops);
> -	if (level == SOL_SOCKET)
> -		err = sock_getsockopt(sock, level, optname, optval, optlen);
> -	else if (unlikely(!ops->getsockopt))
> -		err = -EOPNOTSUPP;
> -	else
> -		err = ops->getsockopt(sock, level, optname, optval,
> -					    optlen);
> -
> -	if (!in_compat_syscall())
> -		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname,
> -						     USER_SOCKPTR(optval),
> -						     USER_SOCKPTR(optlen),
> -						     max_optlen, err);
> -out_put:
>   	fput_light(sock->file, fput_needed);
>   	return err;
>   }