linux-hardening.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: X86 ML <x86@kernel.org>, Josh Poimboeuf <jpoimboe@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	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>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v3 10/16] x86/extable: Mark handlers __cficanonical
Date: Tue, 14 Sep 2021 13:38:47 -0700	[thread overview]
Message-ID: <CABCJKufuv_zNEu1=X+xnUYF6WmFU=ZjSCa0QzDJdUvFSD5gx0A@mail.gmail.com> (raw)
In-Reply-To: <202109141235.BE65491A4@keescook>

On Tue, Sep 14, 2021 at 12:37 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Tue, Sep 14, 2021 at 12:10:39PM -0700, Sami Tolvanen wrote:
> > Exception tables are populated in assembly code, but the handlers are
> > called in fixup_exception, which trips indirect call checking with
> > CONFIG_CFI_CLANG. Mark the handlers __cficanonical to allow addresses
> > taken in assembly to pass CFI checking.
> >
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > ---
> >  arch/x86/mm/extable.c | 64 ++++++++++++++++++++++++-------------------
> >  1 file changed, 36 insertions(+), 28 deletions(-)
> >
> > diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
> > index e1664e9f969c..d16912dcbb4e 100644
> > --- a/arch/x86/mm/extable.c
> > +++ b/arch/x86/mm/extable.c
> > @@ -24,16 +24,18 @@ ex_fixup_handler(const struct exception_table_entry *x)
> >       return (ex_handler_t)((unsigned long)&x->handler + x->handler);
> >  }
> >
> > -__visible bool ex_handler_default(const struct exception_table_entry *fixup,
> > -                               struct pt_regs *regs, int trapnr,
> > -                               unsigned long error_code,
> > -                               unsigned long fault_addr)
> > +__visible __cficanonical
> > +bool ex_handler_default(const struct exception_table_entry *fixup,
> > +                     struct pt_regs *regs, int trapnr,
> > +                     unsigned long error_code,
> > +                     unsigned long fault_addr)
> >  {
> >       regs->ip = ex_fixup_addr(fixup);
> >       return true;
> >  }
> >  EXPORT_SYMBOL(ex_handler_default);
> >
> > +__visible __cficanonical
> >  __visible bool ex_handler_fault(const struct exception_table_entry *fixup,
>
> Double __visible here, but with that fixed:

Ah, thanks for noticing that. I'll fix it in the next version.

>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> I would note that given Linus's recent comments on attribute locations,
> it does seem that __cficanonical is more a function behavior attribute
> than a storage class... I'm not really sure:
> https://lore.kernel.org/mm-commits/CAHk-=wiOCLRny5aifWNhr621kYrJwhfURsa0vFPeUEm8mF0ufg@mail.gmail.com

__visible is not really a storage class either, but I thought it would
make sense to keep these attributes together. I can certainly move
them if anyone has strong feelings about the location.

Sami

  reply	other threads:[~2021-09-14 20:39 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
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 [this message]
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

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='CABCJKufuv_zNEu1=X+xnUYF6WmFU=ZjSCa0QzDJdUvFSD5gx0A@mail.gmail.com' \
    --to=samitolvanen@google.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=jpoimboe@redhat.com \
    --cc=keescook@chromium.org \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=peterz@infradead.org \
    --cc=sedat.dilek@gmail.com \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v3 10/16] x86/extable: Mark handlers __cficanonical' \
    /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

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).