| Message ID | 20200325152629.6904-4-kpsingh@chromium.org |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | MAC and Audit policy using eBPF (KRSI) | expand |
On Wed, Mar 25, 2020 at 04:26:24PM +0100, KP Singh wrote: > From: KP Singh <kpsingh@google.com> > > When CONFIG_BPF_LSM is enabled, nop functions, bpf_lsm_<hook_name>, are > generated for each LSM hook. These functions 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> > Reviewed-by: Kees Cook <keescook@chromium.org> > Acked-by: Yonghong Song <yhs@fb.com> > --- > include/linux/bpf_lsm.h | 22 ++++++++++++++++++++++ > kernel/bpf/bpf_lsm.c | 14 ++++++++++++++ > 2 files changed, 36 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..83b96895829f > --- /dev/null > +++ b/include/linux/bpf_lsm.h > @@ -0,0 +1,22 @@ > +/* 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, DEFAULT, NAME, ...) \ > + RET bpf_lsm_##NAME(__VA_ARGS__); > +#include <linux/lsm_hook_defs.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..1210a819ca52 100644 > --- a/kernel/bpf/bpf_lsm.c > +++ b/kernel/bpf/bpf_lsm.c > @@ -7,6 +7,20 @@ > #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. > + */ > +#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ > +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__) \ I don't think the __weak is needed any more here? > +{ \ > + return DEFAULT; \ I'm impressed that LSM_RET_VOID actually works. :) -Kees > +} > + > +#include <linux/lsm_hook_defs.h> > +#undef LSM_HOOK > > const struct bpf_prog_ops lsm_prog_ops = { > }; > -- > 2.20.1 >
On 25-Mär 12:28, Kees Cook wrote: > On Wed, Mar 25, 2020 at 04:26:24PM +0100, KP Singh wrote: > > From: KP Singh <kpsingh@google.com> > > > > When CONFIG_BPF_LSM is enabled, nop functions, bpf_lsm_<hook_name>, are > > generated for each LSM hook. These functions 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> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > Acked-by: Yonghong Song <yhs@fb.com> > > --- > > include/linux/bpf_lsm.h | 22 ++++++++++++++++++++++ > > kernel/bpf/bpf_lsm.c | 14 ++++++++++++++ > > 2 files changed, 36 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..83b96895829f > > --- /dev/null > > +++ b/include/linux/bpf_lsm.h > > @@ -0,0 +1,22 @@ > > +/* 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, DEFAULT, NAME, ...) \ > > + RET bpf_lsm_##NAME(__VA_ARGS__); > > +#include <linux/lsm_hook_defs.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..1210a819ca52 100644 > > --- a/kernel/bpf/bpf_lsm.c > > +++ b/kernel/bpf/bpf_lsm.c > > @@ -7,6 +7,20 @@ > > #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. > > + */ > > +#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ > > +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__) \ > > I don't think the __weak is needed any more here? This was suggested in: https://lore.kernel.org/bpf/20200221022537.wbmhdfkdbfvw2pww@ast-mbp/ "I think I saw cases when gcc ignored 'noinline' when function is defined in the same file and still performed inlining while keeping the function body. To be safe I think __weak is necessary. That will guarantee noinline." It happened to work nicely with the previous approach for the special hooks but the actual reason for adding the __weak was to guarrantee that these functions don't get inlined. > > > +{ \ > > + return DEFAULT; \ > > I'm impressed that LSM_RET_VOID actually works. :) All the credit goes to Andrii :) - KP > > -Kees > > > +} > > + > > +#include <linux/lsm_hook_defs.h> > > +#undef LSM_HOOK > > > > const struct bpf_prog_ops lsm_prog_ops = { > > }; > > -- > > 2.20.1 > > > > -- > Kees Cook
On Wed, Mar 25, 2020 at 08:39:56PM +0100, KP Singh wrote: > On 25-Mär 12:28, Kees Cook wrote: > > On Wed, Mar 25, 2020 at 04:26:24PM +0100, KP Singh wrote: > > > +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__) \ > > > > I don't think the __weak is needed any more here? > > This was suggested in: > > https://lore.kernel.org/bpf/20200221022537.wbmhdfkdbfvw2pww@ast-mbp/ > > "I think I saw cases when gcc ignored 'noinline' when function is > defined in the same file and still performed inlining while keeping > the function body. To be safe I think __weak is necessary. That will > guarantee noinline." > > It happened to work nicely with the previous approach for the special > hooks but the actual reason for adding the __weak was to guarrantee > that these functions don't get inlined. Oh, hrm. Well, okay. That rationale would imply that the "noinline" macro needs adjustment instead, but that can be separate, something like: include/linux/compiler_attributes.h -#define noinline __attribute__((__noinline__)) +#define noinline __attribute__((__noinline__)) __attribute__((__weak__)) With a comment, etc... -Kees > > > > > > +{ \ > > > + return DEFAULT; \ > > > > I'm impressed that LSM_RET_VOID actually works. :) > > All the credit goes to Andrii :) > > - KP > > > > > -Kees > > > > > +} > > > + > > > +#include <linux/lsm_hook_defs.h> > > > +#undef LSM_HOOK > > > > > > const struct bpf_prog_ops lsm_prog_ops = { > > > }; > > > -- > > > 2.20.1 > > > > > > > -- > > Kees Cook
On 25-Mär 13:07, Kees Cook wrote: > On Wed, Mar 25, 2020 at 08:39:56PM +0100, KP Singh wrote: > > On 25-Mär 12:28, Kees Cook wrote: > > > On Wed, Mar 25, 2020 at 04:26:24PM +0100, KP Singh wrote: > > > > +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__) \ > > > > > > I don't think the __weak is needed any more here? > > > > This was suggested in: > > > > https://lore.kernel.org/bpf/20200221022537.wbmhdfkdbfvw2pww@ast-mbp/ > > > > "I think I saw cases when gcc ignored 'noinline' when function is > > defined in the same file and still performed inlining while keeping > > the function body. To be safe I think __weak is necessary. That will > > guarantee noinline." > > > > It happened to work nicely with the previous approach for the special > > hooks but the actual reason for adding the __weak was to guarrantee > > that these functions don't get inlined. > > Oh, hrm. Well, okay. That rationale would imply that the "noinline" > macro needs adjustment instead, but that can be separate, something like: > > include/linux/compiler_attributes.h > > -#define noinline __attribute__((__noinline__)) > +#define noinline __attribute__((__noinline__)) __attribute__((__weak__)) > > With a comment, etc... Sounds reasonable, I will drop the __weak from this and send a separate patch for this. - KP > > -Kees > > > > > > > > > > +{ \ > > > > + return DEFAULT; \ > > > > > > I'm impressed that LSM_RET_VOID actually works. :) > > > > All the credit goes to Andrii :) > > > > - KP > > > > > > > > -Kees > > > > > > > +} > > > > + > > > > +#include <linux/lsm_hook_defs.h> > > > > +#undef LSM_HOOK > > > > > > > > const struct bpf_prog_ops lsm_prog_ops = { > > > > }; > > > > -- > > > > 2.20.1 > > > > > > > > > > -- > > > Kees Cook > > -- > Kees Cook
diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h new file mode 100644 index 000000000000..83b96895829f --- /dev/null +++ b/include/linux/bpf_lsm.h @@ -0,0 +1,22 @@ +/* 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, DEFAULT, NAME, ...) \ + RET bpf_lsm_##NAME(__VA_ARGS__); +#include <linux/lsm_hook_defs.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..1210a819ca52 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -7,6 +7,20 @@ #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. + */ +#define LSM_HOOK(RET, DEFAULT, NAME, ...) \ +noinline __weak RET bpf_lsm_##NAME(__VA_ARGS__) \ +{ \ + return DEFAULT; \ +} + +#include <linux/lsm_hook_defs.h> +#undef LSM_HOOK const struct bpf_prog_ops lsm_prog_ops = { };