From: KP Singh <kpsingh@chromium.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: open list <linux-kernel@vger.kernel.org>,
bpf <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 v5 3/7] bpf: lsm: provide attachment points for BPF LSM programs
Date: Tue, 24 Mar 2020 23:39:10 +0100 [thread overview]
Message-ID: <20200324223910.GA5448@chromium.org> (raw)
In-Reply-To: <CAEf4BzZZLBf3xRsV4khGCFdTxDFV61KbFfV1mHwM5yiCr4P37w@mail.gmail.com>
On 24-Mär 14:26, Andrii Nakryiko wrote:
> On Tue, Mar 24, 2020 at 9:12 AM KP Singh <kpsingh@chromium.org> wrote:
> >
> > On 24-Mär 11:39, KP Singh wrote:
> > > On 23-Mär 12:59, Andrii Nakryiko wrote:
> > > > On Mon, Mar 23, 2020 at 9:45 AM KP Singh <kpsingh@chromium.org> wrote:
> > > > >
> > > > > From: KP Singh <kpsingh@google.com>
> > > > >
> > > > > When CONFIG_BPF_LSM is enabled, nops functions, bpf_lsm_<hook_name>, are
> > > > > generated for each LSM hook. These nops are initialized as LSM hooks in
> > > > > a subsequent patch.
> > > > >
> > > > > Signed-off-by: KP Singh <kpsingh@google.com>
> > > > > Reviewed-by: Brendan Jackman <jackmanb@google.com>
> > > > > Reviewed-by: Florent Revest <revest@google.com>
> > > > > ---
> > > > > include/linux/bpf_lsm.h | 21 +++++++++++++++++++++
> > > > > kernel/bpf/bpf_lsm.c | 19 +++++++++++++++++++
> > > > > 2 files changed, 40 insertions(+)
> > > > > create mode 100644 include/linux/bpf_lsm.h
> > > > >
> > > > > diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h
> > > > > new file mode 100644
> > > > > index 000000000000..c6423a140220
> > > > > --- /dev/null
> > > > > +++ b/include/linux/bpf_lsm.h
> > > > > @@ -0,0 +1,21 @@
> > > > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > > > +
> > > > > +/*
> > > > > + * Copyright (C) 2020 Google LLC.
> > > > > + */
> > > > > +
> > > > > +#ifndef _LINUX_BPF_LSM_H
> > > > > +#define _LINUX_BPF_LSM_H
> > > > > +
> > > > > +#include <linux/bpf.h>
> > > > > +#include <linux/lsm_hooks.h>
> > > > > +
> > > > > +#ifdef CONFIG_BPF_LSM
> > > > > +
> > > > > +#define LSM_HOOK(RET, NAME, ...) RET bpf_lsm_##NAME(__VA_ARGS__);
> > > > > +#include <linux/lsm_hook_names.h>
> > > > > +#undef LSM_HOOK
> > > > > +
> > > > > +#endif /* CONFIG_BPF_LSM */
> > > > > +
> > > > > +#endif /* _LINUX_BPF_LSM_H */
> > > > > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> > > > > index 82875039ca90..530d137f7a84 100644
> > > > > --- a/kernel/bpf/bpf_lsm.c
> > > > > +++ b/kernel/bpf/bpf_lsm.c
> > > > > @@ -7,6 +7,25 @@
> > > > > #include <linux/filter.h>
> > > > > #include <linux/bpf.h>
> > > > > #include <linux/btf.h>
> > > > > +#include <linux/lsm_hooks.h>
> > > > > +#include <linux/bpf_lsm.h>
> > > > > +
> > > > > +/* For every LSM hook that allows attachment of BPF programs, declare a NOP
> > > > > + * function where a BPF program can be attached as an fexit trampoline.
> > > > > + */
> > > > > +#define LSM_HOOK(RET, NAME, ...) LSM_HOOK_##RET(NAME, __VA_ARGS__)
> > > > > +
> > > > > +#define LSM_HOOK_int(NAME, ...) \
> > > > > +noinline __weak int bpf_lsm_##NAME(__VA_ARGS__) \
> > > > > +{ \
> > > > > + return 0; \
> > > > > +}
> > > > > +
> > > > > +#define LSM_HOOK_void(NAME, ...) \
> > > > > +noinline __weak void bpf_lsm_##NAME(__VA_ARGS__) {}
> > > > > +
> > > >
> > > > Could unify with:
> > > >
> > > > #define LSM_HOOK(RET, NAME, ...) noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__)
> > > > {
> > > > return (RET)0;
> > > > }
> > > >
> > > > then you don't need LSM_HOOK_int and LSM_HOOK_void.
> > >
> > > Nice.
> > >
> > > But, given that we are adding default values and that
> > > they are only needed for int hooks, we will need to keep the macros
> > > separate for int and void. Or, Am I missing a trick here?
> > >
> > > - KP
> >
> > Actually, was able to get it work. not setting a default for void
> > hooks makes the macros messier. So i just set it void. For example:
> >
> > LSM_HOOK(void, void, bprm_committing_creds, struct linux_binprm *bprm)
>
> surprised this works, was going to propose to specify `(void)0` as
> default value :)
Yeah, you are right that does not work. so I added:
LSM_HOOK(void, LSM_RET_VOID, bprm_committed_creds, struct linux_binprm *bprm)
and as you suggested defined LSM_RET_VOID in lsm_hooks.h:
/* LSM_RET_VOID is used as the default value in LSM_HOOK definitions for void
* for void LSM hooks (in include/linux/lsm_hook_defs.h).
*/
#define LSM_RET_VOID ((void) 0)
I also noticed a few other hooks that were passing an initial return
value to call_int_hook which were missed in this revision. Have fixed
these for the next one.
- KP
>
> >
> > This also allows me to use the cleanup you suggested and not having
> > to split every usage into int and void.
> >
>
> Nice, one of the reasons for proposing this.
>
> > - KP
> >
> > >
> > > >
> > > > > +#include <linux/lsm_hook_names.h>
> > > > > +#undef LSM_HOOK
> > > > >
> > > > > const struct bpf_prog_ops lsm_prog_ops = {
> > > > > };
> > > > > --
> > > > > 2.20.1
> > > > >
next prev parent reply other threads:[~2020-03-24 22:39 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 16:44 [PATCH bpf-next v5 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 1/7] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:02 ` Yonghong Song
2020-03-23 16:44 ` [PATCH bpf-next v5 2/7] security: Refactor declaration of LSM hooks KP Singh
2020-03-23 19:33 ` Kees Cook
2020-03-23 19:56 ` Andrii Nakryiko
2020-03-24 16:06 ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 3/7] bpf: lsm: provide attachment points for BPF LSM programs KP Singh
2020-03-23 19:04 ` Yonghong Song
2020-03-23 19:33 ` Kees Cook
2020-03-23 19:59 ` Andrii Nakryiko
2020-03-24 10:39 ` KP Singh
2020-03-24 16:12 ` KP Singh
2020-03-24 21:26 ` Andrii Nakryiko
2020-03-24 22:39 ` KP Singh [this message]
2020-03-23 16:44 ` [PATCH bpf-next v5 4/7] bpf: lsm: Implement attach, detach and execution KP Singh
2020-03-23 19:16 ` Yonghong Song
2020-03-23 19:44 ` KP Singh
2020-03-23 20:18 ` Andrii Nakryiko
2020-03-24 19:00 ` KP Singh
2020-03-24 14:35 ` Stephen Smalley
2020-03-24 14:50 ` KP Singh
2020-03-24 14:58 ` Stephen Smalley
2020-03-24 16:25 ` Casey Schaufler
2020-03-24 17:49 ` Stephen Smalley
2020-03-24 18:01 ` Kees Cook
2020-03-24 18:06 ` KP Singh
2020-03-24 18:21 ` Stephen Smalley
2020-03-24 18:27 ` KP Singh
2020-03-24 18:31 ` KP Singh
2020-03-24 18:34 ` Kees Cook
2020-03-24 18:33 ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks KP Singh
2020-03-23 19:44 ` Kees Cook
2020-03-23 19:47 ` KP Singh
2020-03-23 20:21 ` Andrii Nakryiko
2020-03-23 20:47 ` Casey Schaufler
2020-03-23 21:44 ` Kees Cook
2020-03-23 21:58 ` Casey Schaufler
2020-03-23 22:12 ` Kees Cook
2020-03-23 23:39 ` Casey Schaufler
2020-03-24 1:53 ` KP Singh
2020-03-25 14:35 ` KP Singh
2020-03-24 1:13 ` Casey Schaufler
2020-03-24 1:52 ` KP Singh
2020-03-24 14:37 ` Stephen Smalley
2020-03-24 14:42 ` KP Singh
2020-03-24 14:51 ` Stephen Smalley
2020-03-24 14:51 ` KP Singh
2020-03-24 17:57 ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 6/7] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:21 ` Yonghong Song
2020-03-23 20:25 ` Andrii Nakryiko
2020-03-24 1:57 ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 7/7] bpf: lsm: Add selftests " KP Singh
2020-03-23 20:04 ` Yonghong Song
2020-03-24 20:04 ` KP Singh
2020-03-24 23:54 ` Andrii Nakryiko
2020-03-25 0:36 ` KP Singh
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