Re: [PATCH 2/4] x86: use the correct function type for sys32_(rt_)sigreturn

From: Andy Lutomirski <luto@kernel.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Kees Cook <keescook@chromium.org>, X86 ML <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/4] x86: use the correct function type for sys32_(rt_)sigreturn
Date: Fri, 13 Sep 2019 15:44:42 -0700	[thread overview]
Message-ID: <CALCETrXve9j=fwaH1rNptKB8OPv_wM4QSPoGa2u9qvHFNE8u7A@mail.gmail.com> (raw)
In-Reply-To: <20190913210018.125266-3-samitolvanen@google.com>

On Fri, Sep 13, 2019 at 2:00 PM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> Use the correct function type to avoid tripping Control-Flow
> Integrity (CFI) checking.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
>  arch/x86/ia32/ia32_signal.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> index 1cee10091b9f..878d8998ce6d 100644
> --- a/arch/x86/ia32/ia32_signal.c
> +++ b/arch/x86/ia32/ia32_signal.c
> @@ -118,7 +118,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>         return err;
>  }
>
> -asmlinkage long sys32_sigreturn(void)
> +asmlinkage long sys32_sigreturn(const struct pt_regs *__unused)
>  {
>         struct pt_regs *regs = current_pt_regs();
>         struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
> @@ -144,7 +144,7 @@ asmlinkage long sys32_sigreturn(void)
>         return 0;
>  }
>
> -asmlinkage long sys32_rt_sigreturn(void)
> +asmlinkage long sys32_rt_sigreturn(const struct pt_regs *__unused)
>  {
>         struct pt_regs *regs = current_pt_regs();
>         struct rt_sigframe_ia32 __user *frame;

Shouldn't these be COMPAT_SYSCALL_DEFINE0?

I think you should pick this patch up and add it to your series:

https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/syscalls&id=07daeef08d26728c120ecbe57a55cb5714810b84

with the obvious type fixup, of course.  And then write a little patch
to use COMPAT_SYSCALL_DEFINE0 for rt_sigreturn and sigreturn.

> --
> 2.23.0.237.gc6a4ce50a0-goog
>