Re: [PATCH bpf-next v2 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start
From: Martin KaFai Lau <hidden>
Date: 2021-01-25 23:26:29
Also in:
bpf
On Mon, Jan 25, 2021 at 09:26:40AM -0800, Stanislav Fomichev wrote:
At the moment, BPF_CGROUP_INET{4,6}_BIND hooks can rewrite user_port
to the privileged ones (< ip_unprivileged_port_start), but it will
be rejected later on in the __inet_bind or __inet6_bind.
Let's export 'port_changed' event from the BPF program and bypass
ip_unprivileged_port_start range check when we've seen that
the program explicitly overrode the port. This is accomplished
by generating instructions to set ctx->port_changed along with
updating ctx->user_port.The description requires an update. [ ... ]
quoted hunk ↗ jump to hunk
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index da649f20d6b2..cdf3c7e611d9 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c@@ -1055,6 +1055,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk); * @uaddr: sockaddr struct provided by user * @type: The type of program to be exectuted * @t_ctx: Pointer to attach type specific context + * @flags: Pointer to u32 which contains higher bits of BPF program + * return value (OR'ed together). * * socket is expected to be of type INET or INET6. *@@ -1064,7 +1066,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk); int __cgroup_bpf_run_filter_sock_addr(struct sock *sk, struct sockaddr *uaddr, enum bpf_attach_type type, - void *t_ctx) + void *t_ctx, + u32 *flags) { struct bpf_sock_addr_kern ctx = { .sk = sk,@@ -1087,7 +1090,8 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk, } cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); - ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN); + ret = BPF_PROG_RUN_ARRAY_FLAGS(cgrp->bpf.effective[type], &ctx, + BPF_PROG_RUN, flags); return ret == 1 ? 0 : -EPERM; }diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d0eae51b31e4..ef7c3ca53214 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c@@ -7986,6 +7986,11 @@ static int check_return_code(struct bpf_verifier_env *env) env->prog->expected_attach_type == BPF_CGROUP_INET4_GETSOCKNAME || env->prog->expected_attach_type == BPF_CGROUP_INET6_GETSOCKNAME) range = tnum_range(1, 1); + if (env->prog->expected_attach_type == BPF_CGROUP_INET4_BIND || + env->prog->expected_attach_type == BPF_CGROUP_INET6_BIND) { + range = tnum_range(0, 3); + enforce_attach_type_range = tnum_range(0, 3);
It should be: enforce_attach_type_range = tnum_range(2, 3);