Re: [PATCH net-next v5 07/16] bpf: Add setsockopt helper function to bpf
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2017-07-01 00:01:27
On 06/30/2017 10:06 PM, Lawrence Brakmo wrote: [...]
quoted hunk ↗ jump to hunk
@@ -2672,6 +2673,69 @@ static const struct bpf_func_proto bpf_get_socket_uid_proto = { .arg1_type = ARG_PTR_TO_CTX, }; +BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, + int, level, int, optname, char *, optval, int, optlen) +{ + struct sock *sk = bpf_sock->sk; + int ret = 0; + int val; + + if (!sk_fullsock(sk)) + return -EINVAL; + + if (level == SOL_SOCKET) { + /* Only some socketops are supported */ + val = *((int *)optval); + + switch (optname) { + case SO_RCVBUF: + sk->sk_userlocks |= SOCK_RCVBUF_LOCK; + sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF); + break; + case SO_SNDBUF: + sk->sk_userlocks |= SOCK_SNDBUF_LOCK; + sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF); + break; + case SO_MAX_PACING_RATE: + sk->sk_max_pacing_rate = val; + sk->sk_pacing_rate = min(sk->sk_pacing_rate, + sk->sk_max_pacing_rate); + break; + case SO_PRIORITY: + sk->sk_priority = val; + break; + case SO_RCVLOWAT: + if (val < 0) + val = INT_MAX; + sk->sk_rcvlowat = val ? : 1; + break; + case SO_MARK: + sk->sk_mark = val; + break; + default: + ret = -EINVAL; + } + } else if (level == SOL_TCP && + sk->sk_prot->setsockopt == tcp_setsockopt) { + /* Place holder */ + ret = -EINVAL; + } else { + ret = -EINVAL; + } + return ret; +} + +static const struct bpf_func_proto bpf_setsockopt_proto = { + .func = bpf_setsockopt, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_ANYTHING, + .arg4_type = ARG_PTR_TO_MEM, + .arg5_type = ARG_CONST_SIZE_OR_ZERO,
Hm, I had some feedback on this in your last revision of the patch set [1] that a NULL pointer dereference can be triggered here. Probably oversaw it; I mentioned wrt the above: Any reason you went with the ARG_CONST_SIZE_OR_ZERO type? Semantics of this are that allowed [arg4, arg5] pair can be i) [NULL, 0] or ii) [non-NULL, non-zero], where in case ii) verifier checks that the area is initialized when coming from BPF stack. So above 'val = *((int *)optval);' would give a NULL pointer deref with NULL passed as arg or in case optlen was < sizeof(int) we access stack out of bounds potentially. If the [NULL, 0] pair is not required, I would just make that a ARG_CONST_SIZE and then check for size before accessing optval. Would be good if you could still address it in a most likely final respin. Thanks, Daniel [1] http://patchwork.ozlabs.org/patch/781800/