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Date: Tue, 17 Mar 2015 15:21:36 +0100
From: Borislav Petkov <bp@alien8.de>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>, Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>, Will Drewry <wad@chromium.org>,
        Kees Cook <keescook@chromium.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2 v2] x86/asm/entry/64: Enable interrupts *after* we
 fetch PER_CPU_VAR(old_rsp)
Message-ID: <20150317142136.GH19645@pd.tnic>
References: <1426600344-8254-1-git-send-email-dvlasenk@redhat.com>
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On Tue, Mar 17, 2015 at 02:52:24PM +0100, Denys Vlasenko wrote:
> Without this change, it is still not possible to get rid of
> PER_CPU_VAR(old_rsp) usage in switch_to: if preemption happens
> while we did not fetch PER_CPU_VAR(old_rsp) and stored it in pt_regs->sp,
> PER_CPU_VAR(old_rsp) gets corrupted by other task's user sp.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Ingo Molnar <mingo@kernel.org>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: x86@kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
> 
> Changes since v1: don't try to be clever and use CLBR_RAX
> 
>  arch/x86/kernel/entry_64.S | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Reported-and-tested-by: Borislav Petkov <bp@suse.de>

Thanks Denys!

-- 
Regards/Gruss,
    Boris.

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