On Thu, Jun 30, 2016 at 05:12:10PM -0700, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>
> 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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