From: KP Singh <kpsingh@chromium.org>
To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
James Morris <jmorris@namei.org>,
Kees Cook <keescook@chromium.org>,
Thomas Garnier <thgarnie@chromium.org>,
Michael Halcrow <mhalcrow@google.com>,
Paul Turner <pjt@google.com>,
Brendan Gregg <brendan.d.gregg@gmail.com>,
Jann Horn <jannh@google.com>, Matthew Garrett <mjg59@google.com>,
Christian Brauner <christian@brauner.io>,
Florent Revest <revest@chromium.org>,
Brendan Jackman <jackmanb@chromium.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, "Serge E. Hallyn" <serge@hallyn.com>,
"David S. Miller" <davem@davemloft.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
Stanislav Fomichev <sdf@google.com>,
Quentin Monnet <quentin.monnet@netronome.com>,
Andrey Ignatov <rdna@fb.com>, Joe Stringer <joe@wand.net.nz>
Subject: [PATCH bpf-next v4 3/8] bpf: lsm: provide attachment points for BPF LSM programs
Date: Thu, 20 Feb 2020 18:52:45 +0100 [thread overview]
Message-ID: <20200220175250.10795-4-kpsingh@chromium.org> (raw)
In-Reply-To: <20200220175250.10795-1-kpsingh@chromium.org>
From: KP Singh <kpsingh@google.com>
The BPF LSM programs are implemented as fexit trampolines to avoid the
overhead of retpolines. These programs cannot be attached to security_*
wrappers as there are quite a few security_* functions that do more than
just calling the LSM callbacks.
This was discussed on the lists in:
https://lore.kernel.org/bpf/20200123152440.28956-1-kpsingh@chromium.org/T/#m068becce588a0cdf01913f368a97aea4c62d8266
Adding a NOP callback after all the static LSM callbacks are called has
the following benefits:
- The BPF programs run at the right stage of the security_* wrappers.
- They run after all the static LSM hooks allowed the operation,
therefore cannot allow an action that was already denied.
There are some hooks which do not call call_int_hooks or
call_void_hooks. It's not possible to call the bpf_lsm_* functions
without checking if there is BPF LSM program attached to these hooks.
This is added further in a subsequent patch. For now, these hooks are
marked as NO_BPF (i.e. attachment of BPF programs is not possible).
Signed-off-by: KP Singh <kpsingh@google.com>
---
include/linux/bpf_lsm.h | 34 ++++++++++++++++++++++++++++++++++
kernel/bpf/bpf_lsm.c | 16 ++++++++++++++++
security/security.c | 3 +++
3 files changed, 53 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..f867f72f6aa9
--- /dev/null
+++ b/include/linux/bpf_lsm.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright 2019 Google LLC.
+ */
+
+#ifndef _LINUX_BPF_LSM_H
+#define _LINUX_BPF_LSM_H
+
+#include <linux/bpf.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
+
+#define RUN_BPF_LSM_VOID_PROGS(FUNC, ...) bpf_lsm_##FUNC(__VA_ARGS__)
+#define RUN_BPF_LSM_INT_PROGS(RC, FUNC, ...) ({ \
+ do { \
+ if (RC == 0) \
+ RC = bpf_lsm_##FUNC(__VA_ARGS__); \
+ } while (0); \
+ RC; \
+})
+
+#else /* !CONFIG_BPF_LSM */
+
+#define RUN_BPF_LSM_INT_PROGS(RC, FUNC, ...) (RC)
+#define RUN_BPF_LSM_VOID_PROGS(FUNC, ...)
+
+#endif /* CONFIG_BPF_LSM */
+
+#endif /* _LINUX_BPF_LSM_H */
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index affb6941622e..abc847c9b9a1 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -7,6 +7,22 @@
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/btf.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 int bpf_lsm_##NAME(__VA_ARGS__) \
+{ \
+ return 0; \
+}
+
+#define LSM_HOOK_void(NAME, ...) \
+ noinline void bpf_lsm_##NAME(__VA_ARGS__) {}
+
+#include <linux/lsm_hook_names.h>
+#undef LSM_HOOK
const struct bpf_prog_ops lsm_prog_ops = {
};
diff --git a/security/security.c b/security/security.c
index 565bc9b67276..aa111392a700 100644
--- a/security/security.c
+++ b/security/security.c
@@ -28,6 +28,7 @@
#include <linux/string.h>
#include <linux/msg.h>
#include <net/flow.h>
+#include <linux/bpf_lsm.h>
#define MAX_LSM_EVM_XATTR 2
@@ -684,6 +685,7 @@ static void __init lsm_early_task(struct task_struct *task)
\
hlist_for_each_entry(P, &security_hook_heads.FUNC, list) \
P->hook.FUNC(__VA_ARGS__); \
+ RUN_BPF_LSM_VOID_PROGS(FUNC, __VA_ARGS__); \
} while (0)
#define call_int_hook(FUNC, IRC, ...) ({ \
@@ -696,6 +698,7 @@ static void __init lsm_early_task(struct task_struct *task)
if (RC != 0) \
break; \
} \
+ RC = RUN_BPF_LSM_INT_PROGS(RC, FUNC, __VA_ARGS__); \
} while (0); \
RC; \
})
--
2.20.1
next prev parent reply other threads:[~2020-02-20 17:53 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 17:52 [PATCH bpf-next v4 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-02-20 17:52 ` [PATCH bpf-next v4 1/8] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-02-20 17:52 ` [PATCH bpf-next v4 2/8] security: Refactor declaration of LSM hooks KP Singh
2020-02-20 17:52 ` KP Singh [this message]
2020-02-20 23:49 ` [PATCH bpf-next v4 3/8] bpf: lsm: provide attachment points for BPF LSM programs Casey Schaufler
2020-02-21 11:44 ` KP Singh
2020-02-21 18:23 ` Casey Schaufler
2020-02-22 4:22 ` Kees Cook
2020-02-23 22:08 ` Alexei Starovoitov
2020-02-24 16:32 ` Casey Schaufler
2020-02-24 17:13 ` KP Singh
2020-02-24 18:45 ` Casey Schaufler
2020-02-24 21:41 ` Kees Cook
2020-02-24 22:29 ` Casey Schaufler
2020-02-25 5:41 ` Alexei Starovoitov
2020-02-25 15:31 ` Kees Cook
2020-02-25 19:31 ` KP Singh
2020-02-26 0:30 ` Casey Schaufler
2020-02-26 5:15 ` KP Singh
2020-02-26 15:35 ` Casey Schaufler
2020-02-25 19:29 ` KP Singh
2020-02-24 16:09 ` Casey Schaufler
2020-02-24 17:23 ` KP Singh
2020-02-21 2:25 ` Alexei Starovoitov
2020-02-21 11:47 ` KP Singh
2020-02-20 17:52 ` [PATCH bpf-next v4 4/8] bpf: lsm: Add support for enabling/disabling BPF hooks KP Singh
2020-02-21 18:57 ` Casey Schaufler
2020-02-21 19:11 ` James Morris
2020-02-22 4:26 ` Kees Cook
2020-02-20 17:52 ` [PATCH bpf-next v4 5/8] bpf: lsm: Implement attach, detach and execution KP Singh
2020-02-21 2:17 ` Alexei Starovoitov
2020-02-21 12:02 ` KP Singh
2020-02-20 17:52 ` [PATCH bpf-next v4 6/8] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-02-25 6:45 ` Andrii Nakryiko
2020-02-20 17:52 ` [PATCH bpf-next v4 7/8] bpf: lsm: Add selftests " KP Singh
2020-02-20 17:52 ` [PATCH bpf-next v4 8/8] bpf: lsm: Add Documentation KP Singh
2020-02-21 19:19 ` [PATCH bpf-next v4 0/8] MAC and Audit policy using eBPF (KRSI) Casey Schaufler
2020-02-21 19:41 ` KP Singh
2020-02-21 22:31 ` Casey Schaufler
2020-02-21 23:09 ` KP Singh
2020-02-21 23:49 ` Casey Schaufler
2020-02-22 0:22 ` Kees Cook
2020-02-22 1:04 ` Casey Schaufler
2020-02-22 3:36 ` Kees Cook
2020-02-27 18:40 ` Dr. Greg
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