On 04/30, Daniel Borkmann wrote:
On 4/29/20 7:05 PM, Stanislav Fomichev wrote:
> Currently, bpf_getsocktop and bpf_setsockopt helpers operate on the
> 'struct bpf_sock_ops' context in BPF_PROG_TYPE_SOCK_OPS program.
> Let's generalize them and make the first argument be 'struct bpf_sock'.
> That way, in the future, we can allow those helpers in more places.
>
> BPF_PROG_TYPE_SOCK_OPS still has the existing helpers that operate
> on 'struct bpf_sock_ops', but we add new bpf_{g,s}etsockopt that work
> on 'struct bpf_sock'. [Alternatively, for BPF_PROG_TYPE_SOCK_OPS,
> we can enable them both and teach verifier to pick the right one
> based on the context (bpf_sock_ops vs bpf_sock).]
>
> As an example, let's allow those 'struct bpf_sock' based helpers to
> be called from the BPF_CGROUP_INET{4,6}_CONNECT hooks. That way
> we can override CC before the connection is made.
>
> v2:
> * s/BPF_PROG_TYPE_CGROUP_SOCKOPT/BPF_PROG_TYPE_SOCK_OPS/
>
> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
> Acked-by: Martin KaFai Lau <kafai@xxxxxx>
> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
[...]
> +BPF_CALL_5(bpf_setsockopt, struct sock *, sk,
> + int, level, int, optname, char *, optval, int, optlen)
> +{
> + u32 flags = 0;
> + return _bpf_setsockopt(sk, level, optname, optval, optlen, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_setsockopt_proto = {
> + .func = bpf_setsockopt,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_SOCKET,
> + .arg2_type = ARG_ANYTHING,
> + .arg3_type = ARG_ANYTHING,
> + .arg4_type = ARG_PTR_TO_MEM,
> + .arg5_type = ARG_CONST_SIZE,
> +};
> +
> +BPF_CALL_5(bpf_getsockopt, struct sock *, sk,
> + int, level, int, optname, char *, optval, int, optlen)
> +{
> + return _bpf_getsockopt(sk, level, optname, optval, optlen);
> +}
> +
> static const struct bpf_func_proto bpf_getsockopt_proto = {
> .func = bpf_getsockopt,
> .gpl_only = false,
> .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_SOCKET,
> + .arg2_type = ARG_ANYTHING,
> + .arg3_type = ARG_ANYTHING,
> + .arg4_type = ARG_PTR_TO_UNINIT_MEM,
> + .arg5_type = ARG_CONST_SIZE,
> +};
> +
[...]
> @@ -6043,6 +6098,22 @@ sock_addr_func_proto(enum bpf_func_id func_id,
const struct bpf_prog *prog)
> return &bpf_sk_storage_get_proto;
> case BPF_FUNC_sk_storage_delete:
> return &bpf_sk_storage_delete_proto;
> + case BPF_FUNC_setsockopt:
> + switch (prog->expected_attach_type) {
> + case BPF_CGROUP_INET4_CONNECT:
> + case BPF_CGROUP_INET6_CONNECT:
> + return &bpf_setsockopt_proto;
Hm, I'm not sure this is safe. In the sock_addr_func_proto() we also have
other helpers callable from connect hooks like sk_lookup_{tcp,udp} which
return a PTR_TO_SOCKET_OR_NULL, and now we can pass those sockets also
into
bpf_{get,set}sockopt() helper after lookup to change various sk related
stuff
but w/o being under lock. Doesn't the sock_owned_by_me() yell here at
minimum
(I'd expect so)?
Ugh, good point, I missed the fact that sk_lookup_{tcp,udp} are there
for sock_addr :-( I can try to do a simple test case to verify
that sock_owned_by_me triggers, but I'm pretty certain it should
(I've been calling bpf_{s,g}etsockopt for context socket so it's quiet).
I don't think there is any helper similar to sock_owned_by_me() that
I can call to verify that the socket is held by current thread
(without the lockdep splat) and bail out?
In this case, is something like adding new PTR_TO_LOCKED_SOCKET_OR_NULL
is the way to go? Any other ideas?
