Message-ID: <5538BA21.7000609@redhat.com>
Date: Thu, 23 Apr 2015 11:23:45 +0200
From: Denys Vlasenko <dvlasenk@redhat.com>
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To: Andy Lutomirski <luto@amacapital.net>, Brian Gerst <brgerst@gmail.com>
CC: Steven Rostedt <rostedt@goodmis.org>, Oleg Nesterov <oleg@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>, Will Drewry <wad@chromium.org>,
        =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "linux-tip-commits@vger.kernel.org" 
	<linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS
 to %ss
References: <63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org> <tip-e7d6eefaaa443130079d73cd05039d90b3db7a4a@git.kernel.org> <CAMzpN2gD2kfKaXSYsXjZo=bLQYLk3A-sU_8qizfkp5paRuaePQ@mail.gmail.com> <CALCETrVH6STDwEuLY3gFaNevtjvtOZ7Ox3e10ZhtmitCJnJUKQ@mail.gmail.com>
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On 04/23/2015 10:49 AM, Andy Lutomirski wrote:
> Would fixing this be as simple as changing this code in
> arch/x86/kernel/process.c:
> 
> __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
>         .x86_tss = {
>                 .sp0 = TOP_OF_INIT_STACK,
> #ifdef CONFIG_X86_32
>                 .ss0 = __KERNEL_DS,
> 
> by moving the ifdef down a line?

You can't do that. 64-bit TSS has no .ss0/1/2 fields :)
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