Re: [RFC/PATCH 3/7] [TEMPORARY] x86/entry/32: Sanity check for work_notifysig

From: Andy Lutomirski <luto@amacapital.net>
To: Andy Lutomirski <luto@kernel.org>
Cc: "X86 ML" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Rik van Riel" <riel@redhat.com>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Denys Vlasenko" <vda.linux@googlemail.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Kees Cook" <keescook@chromium.org>,
	"Brian Gerst" <brgerst@gmail.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>
Subject: Re: [RFC/PATCH 3/7] [TEMPORARY] x86/entry/32: Sanity check for work_notifysig
Date: Wed, 8 Jul 2015 12:25:28 -0700	[thread overview]
Message-ID: <CALCETrV2WemO6KqAaixpW2h14h6_b4CRA-Ka889en0UtSoRdYw@mail.gmail.com> (raw)
In-Reply-To: <f5aeb480783ee66b884a38de247d50094c3023fc.1436383168.git.luto@kernel.org>

[cc: Al -- saying I'm cc-ing you in the patch 0 description doesn't make it so.]

On Wed, Jul 8, 2015 at 12:24 PM, Andy Lutomirski <luto@kernel.org> wrote:
> 44fbbb3dc687c added an unnecessary check.  Add a temporary assertion
> to confirm that it's unnecessary.
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  arch/x86/entry/entry_32.S | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
> index a36d5df6a749..d36afad80ad1 100644
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -491,10 +491,13 @@ work_notifysig:                                   # deal with pending signals and
>  #endif
>         TRACE_IRQS_ON
>         ENABLE_INTERRUPTS(CLBR_NONE)
> +       /* Temporary sanity check */
>         movb    PT_CS(%esp), %bl
>         andb    $SEGMENT_RPL_MASK, %bl
>         cmpb    $USER_RPL, %bl
> -       jb      resume_kernel
> +       jnb     2f
> +       ud2
> +2:
>         xorl    %edx, %edx
>         call    do_notify_resume
>         jmp     resume_userspace
> --
> 2.4.3
>


-- 
Andy Lutomirski
AMA Capital Management, LLC