From: Sami Tolvanen <samitolvanen@google.com>
To: Peter Zijlstra <peterz@infradead.org>
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 13:29:02 -0700 [thread overview]
Message-ID: <CABCJKud1Gm0ouROKLAw9t03qbs+_EASky053=SqijPJahqogng@mail.gmail.com> (raw)
In-Reply-To: <20211005065923.GH4323@worktop.programming.kicks-ass.net>
On Mon, Oct 4, 2021 at 11:59 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> 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.
Good point. I read through the latest arm64 static call proposal and
while it can fall back to an indirect call, it doesn't look like that
would cause issues with CFI.
> (and just in case you care about CFI on PPC32, they too grew basic
> static_call support)
We are currently targeting only x86_64 and arm64, but I'll keep that
in mind in case we want to add more platforms.
Sami
next prev parent reply other threads:[~2021-10-05 20:29 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
2021-10-05 20:29 ` Sami Tolvanen [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CABCJKud1Gm0ouROKLAw9t03qbs+_EASky053=SqijPJahqogng@mail.gmail.com' \
--to=samitolvanen@google.com \
--cc=jpoimboe@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=llvm@lists.linux.dev \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=sedat.dilek@gmail.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).