From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: KP Singh <kpsingh@chromium.org>
Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org,
Brendan Jackman <jackmanb@google.com>,
Florent Revest <revest@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
James Morris <jmorris@namei.org>,
Kees Cook <keescook@chromium.org>, Paul Turner <pjt@google.com>,
Jann Horn <jannh@google.com>,
Florent Revest <revest@chromium.org>,
Brendan Jackman <jackmanb@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution
Date: Thu, 26 Mar 2020 20:12:56 -0700 [thread overview]
Message-ID: <20200327031256.vhk2luomxgex3ui4@ast-mbp> (raw)
In-Reply-To: <20200326142823.26277-5-kpsingh@chromium.org>
On Thu, Mar 26, 2020 at 03:28:19PM +0100, KP Singh wrote:
>
> if (arg == nr_args) {
> - if (prog->expected_attach_type == BPF_TRACE_FEXIT) {
> + /* BPF_LSM_MAC programs only have int and void functions they
> + * can be attached to. When they are attached to a void function
> + * they result in the creation of an FEXIT trampoline and when
> + * to a function that returns an int, a MODIFY_RETURN
> + * trampoline.
> + */
> + if (prog->expected_attach_type == BPF_TRACE_FEXIT ||
> + prog->expected_attach_type == BPF_LSM_MAC) {
> if (!t)
> return true;
> t = btf_type_by_id(btf, t->type);
Could you add a comment here that though BPF_MODIFY_RETURN-like check
if (ret_type != 'int') return -EINVAL;
is _not_ done here. It is still safe, since LSM hooks have only
void and int return types.
> + case BPF_LSM_MAC:
> + if (!prog->aux->attach_func_proto->type)
> + /* The function returns void, we cannot modify its
> + * return value.
> + */
> + return BPF_TRAMP_FEXIT;
> + else
> + return BPF_TRAMP_MODIFY_RETURN;
I was thinking whether it would help performance significantly enough
if we add a flavor of BPF_TRAMP_FEXIT that doesn't have
BPF_TRAMP_F_CALL_ORIG.
That will save the cost of nop call, but I guess indirect call due
to lsm infra is slow enough, so this extra few cycles won't be noticeable.
So I'm fine with it as-is. When lsm hooks will get rid of indirect call
we can optimize it further.
next prev parent reply other threads:[~2020-03-27 3:13 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 14:28 [PATCH bpf-next v7 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-03-26 14:28 ` [PATCH bpf-next v7 1/8] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-03-27 0:27 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 2/8] security: Refactor declaration of LSM hooks KP Singh
2020-03-27 0:28 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 3/8] bpf: lsm: provide attachment points for BPF LSM programs KP Singh
2020-03-27 0:29 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution KP Singh
2020-03-26 19:12 ` Andrii Nakryiko
2020-03-26 19:39 ` KP Singh
2020-03-27 0:24 ` James Morris
2020-03-27 12:27 ` Stephen Smalley
2020-03-27 12:41 ` KP Singh
2020-03-27 13:43 ` Stephen Smalley
2020-03-27 14:29 ` KP Singh
2020-03-27 16:36 ` Casey Schaufler
2020-03-27 18:59 ` Kees Cook
2020-03-27 19:17 ` KP Singh
2020-03-27 3:12 ` Alexei Starovoitov [this message]
2020-03-27 15:06 ` KP Singh
2020-03-26 14:28 ` [PATCH bpf-next v7 5/8] bpf: lsm: Initialize the BPF LSM hooks KP Singh
2020-03-27 0:29 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 6/8] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-03-27 0:30 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 7/8] bpf: lsm: Add selftests " KP Singh
2020-03-26 19:24 ` Andrii Nakryiko
2020-03-26 19:44 ` KP Singh
2020-03-27 0:31 ` James Morris
2020-03-26 14:28 ` [PATCH bpf-next v7 8/8] bpf: lsm: Add Documentation KP Singh
2020-03-26 19:31 ` Andrii Nakryiko
2020-03-26 20:56 ` KP Singh
2020-03-26 22:01 ` Andrii Nakryiko
2020-03-27 0:33 ` James Morris
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