From: Andy Lutomirski <luto@amacapital.net>
To: Borislav Petkov <bp@alien8.de>
Cc: Michal Hocko <mhocko@suse.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
stable <stable@vger.kernel.org>, Andi Kleen <ak@linux.intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
X86 ML <x86@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dave Hansen <dave@sr71.net>
Subject: Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro
Date: Fri, 1 Jul 2016 09:30:37 -0700 [thread overview]
Message-ID: <CALCETrV+uq4fcgmUK_u6_Tu6Ex3FrYM0fQjDbjwy5KZ8f8OuHg@mail.gmail.com> (raw)
In-Reply-To: <20160701092300.GD4593@pd.tnic>
On Jul 1, 2016 2:23 AM, "Borislav Petkov" <bp@alien8.de> wrote:
>
> On Thu, Jun 30, 2016 at 05:12:10PM -0700, Dave Hansen wrote:
> >
> > From: Dave Hansen <dave.hansen@linux.intel.com>
> >
> > epufeatures.h currently defines X86_BUG(9) twice on 32-bit:
> >
> > #define X86_BUG_NULL_SEG X86_BUG(9) /* Nulling a selector preserves the base */
> > ...
> > #ifdef CONFIG_X86_32
> > #define X86_BUG_ESPFIX X86_BUG(9) /* "" IRET to 16-bit SS corrupts ESP/RSP high bits */
> > #endif
> >
> > I think what happened was that this added the X86_BUG_ESPFIX, but
> > in an #ifdef below most of the bugs:
> >
> > [58a5aac5] x86/entry/32: Introduce and use X86_BUG_ESPFIX instead of paravirt_enabled
> >
> > Then this came along and added X86_BUG_NULL_SEG, but collided
> > with the earlier one that did the bug below the main block
> > defining all the X86_BUG()s.
> >
> > [7a5d6704] x86/cpu: Probe the behavior of nulling out a segment at boot time
> >
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> > Acked-by: Andy Lutomirski <luto@kernel.org>
> > Cc: stable@vger.kernel.org
> > ---
> >
> > b/arch/x86/include/asm/cpufeatures.h | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff -puN arch/x86/include/asm/cpufeatures.h~knl-leak-10-fix-x86-bugs-macros arch/x86/include/asm/cpufeatures.h
> > --- a/arch/x86/include/asm/cpufeatures.h~knl-leak-10-fix-x86-bugs-macros 2016-06-30 17:10:41.215185869 -0700
> > +++ b/arch/x86/include/asm/cpufeatures.h 2016-06-30 17:10:41.218186005 -0700
> > @@ -301,10 +301,6 @@
> > #define X86_BUG_FXSAVE_LEAK X86_BUG(6) /* FXSAVE leaks FOP/FIP/FOP */
> > #define X86_BUG_CLFLUSH_MONITOR X86_BUG(7) /* AAI65, CLFLUSH required before MONITOR */
> > #define X86_BUG_SYSRET_SS_ATTRS X86_BUG(8) /* SYSRET doesn't fix up SS attrs */
> > -#define X86_BUG_NULL_SEG X86_BUG(9) /* Nulling a selector preserves the base */
> > -#define X86_BUG_SWAPGS_FENCE X86_BUG(10) /* SWAPGS without input dep on GS */
> > -
> > -
> > #ifdef CONFIG_X86_32
> > /*
> > * 64-bit kernels don't use X86_BUG_ESPFIX. Make the define conditional
>
> So I'd remove the "#ifdef CONFIG_X86_32" ifdeffery too and make that bit
> unconditional - so what, we have enough free bits. But I'd leave the
> comment to still avoid the confusion :)
>
I put the ifdef there to prevent anyone from accidentally using it in
a 64-bit code path, not to save a bit. We could put in the middle of
the list to make the mistake much less likely to be repeated, I
suppose.
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next prev parent reply other threads:[~2016-07-01 16:30 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-01 0:12 [PATCH 0/6] [v3] Workaround for Xeon Phi PTE A/D bits erratum Dave Hansen
2016-07-01 0:12 ` [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Dave Hansen
2016-07-01 9:23 ` Borislav Petkov
2016-07-01 16:30 ` Andy Lutomirski [this message]
2016-07-01 16:46 ` Borislav Petkov
2016-07-03 14:36 ` Andy Lutomirski
2016-07-03 18:44 ` Borislav Petkov
2016-07-01 0:12 ` [PATCH 2/6] mm, tlb: add mmu_gather->saw_unset_a_or_d Dave Hansen
2016-07-01 0:12 ` [PATCH 3/6] mm: add force_batch_flush to mmu_gather Dave Hansen
2016-07-01 0:12 ` [PATCH 4/6] mm: move flush in madvise_free_pte_range() Dave Hansen
2016-07-01 0:12 ` [PATCH 5/6] mm: make tlb_flush_mmu_tlbonly() return whether it flushed Dave Hansen
2016-07-01 0:12 ` [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs Dave Hansen
2016-07-01 1:50 ` Nadav Amit
2016-07-01 1:54 ` Dave Hansen
2016-07-01 2:55 ` Linus Torvalds
2016-07-01 3:06 ` Brian Gerst
2016-07-01 3:21 ` Linus Torvalds
2016-07-03 17:10 ` Dave Hansen
2016-07-01 4:39 ` Dave Hansen
2016-07-01 5:43 ` Linus Torvalds
2016-07-01 14:25 ` Eric W. Biederman
2016-07-01 15:51 ` Dave Hansen
2016-07-01 18:12 ` Eric W. Biederman
2016-07-01 16:07 ` Linus Torvalds
2016-07-01 16:14 ` Dave Hansen
2016-07-01 16:25 ` Linus Torvalds
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