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Groups > linux.kernel > #1434923 > unrolled thread
| Started by | Dave Hansen <dave@sr71.net> |
|---|---|
| First post | 2016-07-01 02:20 +0200 |
| Last post | 2016-07-03 20:50 +0200 |
| Articles | 6 — 3 participants |
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[PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Dave Hansen <dave@sr71.net> - 2016-07-01 02:20 +0200
Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Borislav Petkov <bp@alien8.de> - 2016-07-01 11:50 +0200
Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Andy Lutomirski <luto@amacapital.net> - 2016-07-01 18:40 +0200
Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Borislav Petkov <bp@alien8.de> - 2016-07-01 18:50 +0200
Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Andy Lutomirski <luto@amacapital.net> - 2016-07-03 16:40 +0200
Re: [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro Borislav Petkov <bp@alien8.de> - 2016-07-03 20:50 +0200
| From | Dave Hansen <dave@sr71.net> |
|---|---|
| Date | 2016-07-01 02:20 +0200 |
| Subject | [PATCH 1/6] x86: fix duplicated X86_BUG(9) macro |
| Message-ID | <rPUlz-7QC-11@gated-at.bofh.it> |
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 @@ -312,5 +308,7 @@ */ #define X86_BUG_ESPFIX X86_BUG(9) /* "" IRET to 16-bit SS corrupts ESP/RSP high bits */ #endif +#define X86_BUG_NULL_SEG X86_BUG(10) /* Nulling a selector preserves the base */ +#define X86_BUG_SWAPGS_FENCE X86_BUG(11) /* SWAPGS without input dep on GS */ #endif /* _ASM_X86_CPUFEATURES_H */ _
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| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Date | 2016-07-01 11:50 +0200 |
| Message-ID | <rQ3fc-4Yz-17@gated-at.bofh.it> |
| In reply to | #1434923 |
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 :)
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-07-01 18:40 +0200 |
| Message-ID | <rQ9DX-ug-11@gated-at.bofh.it> |
| In reply to | #1435213 |
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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| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Date | 2016-07-01 18:50 +0200 |
| Message-ID | <rQ9ND-xE-5@gated-at.bofh.it> |
| In reply to | #1435490 |
On Fri, Jul 01, 2016 at 09:30:37AM -0700, Andy Lutomirski wrote:
> 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.
Well, if someone does, someone will notice pretty soon, no?
I just don't see the reason to worry but maybe I'm missing it.
And we can call it X86_BUG_ESPFIX_X86_32 or so too...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-07-03 16:40 +0200 |
| Message-ID | <rQQIV-1mL-15@gated-at.bofh.it> |
| In reply to | #1435495 |
On Jul 1, 2016 9:47 AM, "Borislav Petkov" <bp@alien8.de> wrote: > > On Fri, Jul 01, 2016 at 09:30:37AM -0700, Andy Lutomirski wrote: > > 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. > > Well, if someone does, someone will notice pretty soon, no? Dunno. ESPFIX was broken under KVM for years and no one notices. > > I just don't see the reason to worry but maybe I'm missing it. > > And we can call it X86_BUG_ESPFIX_X86_32 or so too... We could do that, too, I guess. But the current solution is only two extra lines of code. We could reorder the things so that it's in the middle instead of at the end, I suppose. --Andy
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| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Date | 2016-07-03 20:50 +0200 |
| Message-ID | <rQUCR-3Hu-17@gated-at.bofh.it> |
| In reply to | #1435969 |
On Sun, Jul 03, 2016 at 07:36:30AM -0700, Andy Lutomirski wrote:
> Dunno. ESPFIX was broken under KVM for years and no one notices.
Ah, so this really was the case already. :-\
> We could do that, too, I guess. But the current solution is only two
> extra lines of code. We could reorder the things so that it's in the
> middle instead of at the end, I suppose.
Yeah, sounds good. Especially if it was already broken - I missed that
fact.
Thanks.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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