From: Peter Zijlstra <peterz@infradead.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: X86 ML <x86@kernel.org>, Kees Cook <keescook@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
linux-hardening@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
llvm@lists.linux.dev
Subject: Re: [PATCH v4 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB
Date: Tue, 5 Oct 2021 08:59:23 +0200 [thread overview]
Message-ID: <20211005065923.GH4323@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CABCJKudBrHfwR=gQc=9=cfBjR9p5jm65ovSNwzLLEpDUdo6ZPQ@mail.gmail.com>
On Mon, Oct 04, 2021 at 12:10:46PM -0700, Sami Tolvanen wrote:
> On Mon, Oct 4, 2021 at 6:50 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > Why DEFINE_CFI_IMMEDIATE_RETURN_STUB() vs __no_cfi attribute that we can
> > stick on the relvant functions?
>
> To avoid accidentally creating useful gadgets for attackers. For
> example, while excluding an empty stub isn't necessarily ideal,
> allowing calls to a function that always returns zero would be worse.
I was afraid you'd say something like that...
> > Because I've got at least one more variant for you :-) See
> > kernel/static_call.c:__static_call_return0
>
> Does __static_call_return0 ever get called indirectly on architectures
> that support static calls? If it's always patched into a direct call,
> the type mismatch isn't an issue.
For x86_64 it should indeed never get called, however if you plan on
supporting i386 then you need the annotation. Also, it might get called
on arm64 which is about to grow basic HAVE_STATIC_CALL support.
(and just in case you care about CFI on PPC32, they too grew basic
static_call support)
next prev parent reply other threads:[~2021-10-05 6:59 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 18:05 [PATCH v4 00/15] x86: Add support for Clang CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 01/15] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-09-30 18:40 ` Nick Desaulniers
2021-10-06 3:36 ` Josh Poimboeuf
2021-10-06 16:18 ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 02/15] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-10-06 3:37 ` Josh Poimboeuf
2021-09-30 18:05 ` [PATCH v4 03/15] linkage: Add DECLARE_ASM_FUNC_SYMBOL Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Sami Tolvanen
2021-09-30 18:50 ` Nick Desaulniers
2021-10-01 20:07 ` Sami Tolvanen
2021-10-04 13:50 ` Peter Zijlstra
2021-10-04 19:10 ` Sami Tolvanen
2021-10-05 6:59 ` Peter Zijlstra [this message]
2021-10-05 20:29 ` Sami Tolvanen
2021-10-05 20:56 ` Peter Zijlstra
2021-10-05 21:53 ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 05/15] tracepoint: Exclude tp_stub_func from CFI checking Sami Tolvanen
2021-09-30 18:50 ` Nick Desaulniers
2021-10-01 20:08 ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 06/15] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-10-06 3:29 ` Josh Poimboeuf
2021-10-06 13:02 ` Steven Rostedt
2021-10-06 13:54 ` Josh Poimboeuf
2021-10-06 14:16 ` Steven Rostedt
2021-10-06 16:31 ` Sami Tolvanen
2021-10-06 16:58 ` Steven Rostedt
2021-10-06 17:45 ` Sami Tolvanen
2021-10-06 20:43 ` Josh Poimboeuf
2021-10-06 21:10 ` Steven Rostedt
2021-10-06 21:23 ` Josh Poimboeuf
2021-10-06 23:14 ` Sami Tolvanen
2021-10-07 0:56 ` Steven Rostedt
2021-09-30 18:05 ` [PATCH v4 07/15] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 08/15] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 09/15] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 10/15] x86/purgatory: Disable CFI Sami Tolvanen
2021-09-30 19:05 ` Nick Desaulniers
2021-09-30 18:05 ` [PATCH v4 11/15] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-10-06 3:31 ` Josh Poimboeuf
2021-10-06 16:17 ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 12/15] x86, module: " Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 13/15] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 14/15] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 15/15] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
2021-09-30 18:38 ` [PATCH v4 00/15] x86: Add support for Clang CFI Nick Desaulniers
2021-10-05 20:36 ` Josh Poimboeuf
2021-10-05 21:52 ` Sami Tolvanen
2021-10-06 2:42 ` Josh Poimboeuf
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