Re: [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks
From: Kees Cook <hidden>
Date: 2020-03-23 19:44:44
Also in:
bpf, lkml
On Mon, Mar 23, 2020 at 05:44:13PM +0100, KP Singh wrote:
From: KP Singh <redacted> The bpf_lsm_ nops are initialized into the LSM framework like any other LSM. Some LSM hooks do not have 0 as their default return value. The __weak symbol for these hooks is overridden by a corresponding definition in security/bpf/hooks.c The LSM can be enabled / disabled with CONFIG_LSM. Signed-off-by: KP Singh <redacted>
Nice! This is super clean on the LSM side of things. :) One note below...
quoted hunk ↗ jump to hunk
Reviewed-by: Brendan Jackman <jackmanb@google.com> Reviewed-by: Florent Revest <redacted> --- security/Kconfig | 10 ++++---- security/Makefile | 2 ++ security/bpf/Makefile | 5 ++++ security/bpf/hooks.c | 55 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 67 insertions(+), 5 deletions(-) create mode 100644 security/bpf/Makefile create mode 100644 security/bpf/hooks.cdiff --git a/security/Kconfig b/security/Kconfig index 2a1a2d396228..cd3cc7da3a55 100644 --- a/security/Kconfig +++ b/security/Kconfig@@ -277,11 +277,11 @@ endchoice config LSM string "Ordered list of enabled LSMs" - default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor" if DEFAULT_SECURITY_SMACK - default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo" if DEFAULT_SECURITY_APPARMOR - default "lockdown,yama,loadpin,safesetid,integrity,tomoyo" if DEFAULT_SECURITY_TOMOYO - default "lockdown,yama,loadpin,safesetid,integrity" if DEFAULT_SECURITY_DAC - default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor" + default "lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK + default "lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR + default "lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO + default "lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC + default "lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf" help A comma-separated list of LSMs, in initialization order. Any LSMs left off this list will be ignored. This can bediff --git a/security/Makefile b/security/Makefile index 746438499029..22e73a3482bd 100644 --- a/security/Makefile +++ b/security/Makefile@@ -12,6 +12,7 @@ subdir-$(CONFIG_SECURITY_YAMA) += yama subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown +subdir-$(CONFIG_BPF_LSM) += bpf # always enable default capabilities obj-y += commoncap.o@@ -30,6 +31,7 @@ obj-$(CONFIG_SECURITY_LOADPIN) += loadpin/ obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o +obj-$(CONFIG_BPF_LSM) += bpf/ # Object integrity file lists subdir-$(CONFIG_INTEGRITY) += integritydiff --git a/security/bpf/Makefile b/security/bpf/Makefile new file mode 100644 index 000000000000..c7a89a962084 --- /dev/null +++ b/security/bpf/Makefile@@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) 2020 Google LLC. + +obj-$(CONFIG_BPF_LSM) := hooks.odiff --git a/security/bpf/hooks.c b/security/bpf/hooks.c new file mode 100644 index 000000000000..68e5824868f9 --- /dev/null +++ b/security/bpf/hooks.c@@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2020 Google LLC. + */ +#include <linux/lsm_hooks.h> +#include <linux/bpf_lsm.h> + +/* Some LSM hooks do not have 0 as their default return values. Override the + * __weak definitons generated by default for these hooks
If you wanted to avoid this, couldn't you make the default return value
part of lsm_hooks.h?
e.g.:
LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct inode *inode,
const char *name, void **buffer, bool alloc)
...
#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
LSM_HOOK_##RET(NAME, DEFAULT, __VA_ARGS__)
...
#define LSM_HOOK_int(NAME, DEFAULT, ...) \
noinline int bpf_lsm_##NAME(__VA_ARGS__) \
{ \
return (DEFAULT); \
}
Then all the __weak stuff is gone, and the following 4 functions don't
need to be written out, and the information is available to the macros
if anyone else might ever want it.
-Kees
+ */
+noinline int bpf_lsm_inode_getsecurity(struct inode *inode, const char *name,
+ void **buffer, bool alloc)
+{
+ return -EOPNOTSUPP;
+}
+
+noinline int bpf_lsm_inode_setsecurity(struct inode *inode, const char *name,
+ const void *value, size_t size,
+ int flags)
+{
+ return -EOPNOTSUPP;
+}
+
+noinline int bpf_lsm_task_prctl(int option, unsigned long arg2,
+ unsigned long arg3, unsigned long arg4,
+ unsigned long arg5)
+{
+ return -ENOSYS;
+}
+
+noinline int bpf_lsm_xfrm_state_pol_flow_match(struct xfrm_state *x,
+ struct xfrm_policy *xp,
+ const struct flowi *fl)
+{
+ return 1;
+}
+
+static struct security_hook_list bpf_lsm_hooks[] __lsm_ro_after_init = {
+ #define LSM_HOOK(RET, NAME, ...) LSM_HOOK_INIT(NAME, bpf_lsm_##NAME),
+ #include <linux/lsm_hook_names.h>
+ #undef LSM_HOOK
+};
+
+static int __init bpf_lsm_init(void)
+{
+ security_add_hooks(bpf_lsm_hooks, ARRAY_SIZE(bpf_lsm_hooks), "bpf");
+ pr_info("LSM support for eBPF active\n");
+ return 0;
+}
+
+DEFINE_LSM(bpf) = {
+ .name = "bpf",
+ .init = bpf_lsm_init,
+};
--
2.20.1-- Kees Cook