From: Sami Tolvanen <samitolvanen@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: X86 ML <x86@kernel.org>, Kees Cook <keescook@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Nathan Chancellor <nathan@kernel.org>,
Sedat Dilek <sedat.dilek@gmail.com>,
linux-hardening@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v3 04/16] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB
Date: Tue, 14 Sep 2021 13:32:34 -0700 [thread overview]
Message-ID: <CABCJKuc1LNPfO=RBDpOahGBgc7TF1L4D_ujhbrNfFWJaExsjpQ@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdnTeTLcrjPy5QcshSLr0Cc2uj7_hTt70j37eEBZzxr=PA@mail.gmail.com>
On Tue, Sep 14, 2021 at 12:36 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Sep 14, 2021 at 12:10 PM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > This change introduces the DEFINE_CFI_IMMEDIATE_RETURN_STUB macro,
> > which defines a stub function that immediately returns and when
> > defined in the core kernel, always passes indirect call checking
> > with CONFIG_CFI_CLANG. Note that this macro should only be used when
> > a stub cannot be called using the correct function type.
> >
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > ---
> > include/asm-generic/vmlinux.lds.h | 11 +++++++++++
> > include/linux/cfi.h | 14 ++++++++++++++
> > kernel/cfi.c | 24 +++++++++++++++++++++++-
> > 3 files changed, 48 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index f2984af2b85b..5b77284f7221 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -407,6 +407,16 @@
> > KEEP(*(.static_call_tramp_key)) \
> > __stop_static_call_tramp_key = .;
> >
> > +#ifdef CONFIG_CFI_CLANG
> > +#define CFI_EXCLUDED_DATA \
> > + . = ALIGN(8); \
> > + __start_cfi_excluded = .; \
> > + KEEP(*(.cfi_excluded_stubs)) \
> > + __stop_cfi_excluded = .;
> > +#else
> > +#define CFI_EXCLUDED_DATA
> > +#endif
> > +
> > /*
> > * Allow architectures to handle ro_after_init data on their
> > * own by defining an empty RO_AFTER_INIT_DATA.
> > @@ -430,6 +440,7 @@
> > __start_rodata = .; \
> > *(.rodata) *(.rodata.*) \
> > SCHED_DATA \
> > + CFI_EXCLUDED_DATA \
> > RO_AFTER_INIT_DATA /* Read only after init */ \
> > . = ALIGN(8); \
> > __start___tracepoints_ptrs = .; \
> > diff --git a/include/linux/cfi.h b/include/linux/cfi.h
> > index 879744aaa6e0..9ebf67a0d421 100644
> > --- a/include/linux/cfi.h
> > +++ b/include/linux/cfi.h
> > @@ -20,6 +20,18 @@ extern void __cfi_check(uint64_t id, void *ptr, void *diag);
> > #define __CFI_ADDRESSABLE(fn, __attr) \
> > const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn
> >
> > +/*
> > + * Defines a stub function that returns immediately, and when defined and
> > + * referenced in the core kernel, always passes CFI checking. This should
> > + * be used only for stubs that cannot be called using the correct function
> > + * pointer type, which should be rare.
> > + */
> > +#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \
> > + void fn(void) { return; } \
> > + const void *__cfi_excl_ ## fn __visible \
> > + __attribute__((__section__(".cfi_excluded_stubs"))) \
>
> Can we use __section from include/linux/compiler_attributes.h here
> rather than open coding the function attribute?
Sure. I'll change this in v4.
Sami
next prev parent reply other threads:[~2021-09-14 20:32 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-14 19:10 [PATCH v3 00/16] x86: Add support for Clang CFI Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 01/16] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-09-14 19:29 ` Nick Desaulniers
2021-09-14 21:01 ` Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 02/16] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 03/16] linkage: Add DECLARE_ASM_FUNC_SYMBOL Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 04/16] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Sami Tolvanen
2021-09-14 19:36 ` Nick Desaulniers
2021-09-14 20:32 ` Sami Tolvanen [this message]
2021-09-14 19:10 ` [PATCH v3 05/16] tracepoint: Exclude tp_stub_func from CFI checking Sami Tolvanen
2021-09-14 19:39 ` Nick Desaulniers
2021-09-14 19:10 ` [PATCH v3 06/16] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 07/16] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-09-14 19:30 ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 08/16] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-09-14 19:32 ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 09/16] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-14 19:33 ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 10/16] x86/extable: Mark handlers __cficanonical Sami Tolvanen
2021-09-14 19:37 ` Kees Cook
2021-09-14 20:38 ` Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 11/16] x86/purgatory: Disable CFI Sami Tolvanen
2021-09-14 20:02 ` Nick Desaulniers
2021-09-14 20:30 ` Sami Tolvanen
2021-09-14 22:31 ` Nick Desaulniers
2021-09-15 6:24 ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 12/16] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 13/16] x86, module: " Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 14/16] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-09-14 19:44 ` Kees Cook
2021-09-14 19:46 ` Nick Desaulniers
2021-09-14 19:10 ` [PATCH v3 15/16] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-09-14 19:40 ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 16/16] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
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