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    SubjectRe: [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks
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    On 3/23/2020 9:44 AM, KP Singh wrote:
    > From: KP Singh <kpsingh@google.com>
    >
    > 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 <kpsingh@google.com>
    > Reviewed-by: Brendan Jackman <jackmanb@google.com>
    > Reviewed-by: Florent Revest <revest@google.com>
    > ---
    > 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.c
    >
    > diff --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 be
    > diff --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-$(CONFIG_INTEGRITY) += integrity
    > diff --git a/security/bpf/Makefile b/security/bpf/Makefile
    > new file mode 100644
    > index 000000000000..c7a89a962084
    > --- /dev/null
    > +++ b/security/bpf/Makefile
    > @@ -0,0 +1,5 @@
    > +# SPDX-License-Identifier: GPL-2.0
    > +#
    > +# Copyright (C) 2020 Google LLC.
    > +
    > +obj-$(CONFIG_BPF_LSM) := hooks.o
    > diff --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
    > + */
    > +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,

    Have you given up on the "BPF must be last" requirement?

    > +};

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