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* [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header
@ 2017-02-16 22:14 Yu-cheng Yu
  0 siblings, 0 replies; 4+ messages in thread
From: Yu-cheng Yu @ 2017-02-16 22:14 UTC (permalink / raw)
  To: linux-kernel, x86, H. Peter Anvin, Thomas Gleixner, Ingo Molnar,
	stable, Borislav Petkov, Dave Hansen, haokexin, Fenghua Yu,
	Ravi V. Shankar, peterz, Andy Lutomirski, Joakim Tjernlund,
	torvalds, Greg Kroah-Hartman
  Cc: Yu-cheng Yu

This is essentially the same patch as:

  commit dffba9a31c77 ("x86/fpu/xstate: Fix xcomp_bv in XSAVES header")

in the upstream tree, rebased and tested for the stable tree.
This can be applied to both linux-stable-rc/linux-4.9.y and
linux-stable-rc/linux-4.8.y if desired. 

The compacted-format XSAVES area is determined at boot time and
never changed after.  The field xsave.header.xcomp_bv indicates
which components are in the fixed XSAVES format.

In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
format since at the time there is no valid data.

However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
as in commit

  b22cbe404a9c ("x86/fpu: Fix invalid FPU ptrace state after execve()")

and when __fpu_restore_sig() does fpu__restore() for a COMPAT-mode
app, a #GP occurs.  This can be easily triggered by doing valgrind on
a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
others:

	https://bugzilla.kernel.org/show_bug.cgi?id=190061

Fix it by setting xcomp_bv correctly.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
---
 arch/x86/kernel/fpu/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index ebb4e95..96d80df 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -236,7 +236,8 @@ void fpstate_init(union fpregs_state *state)
 	 * it will #GP. Make sure it is replaced after the memset().
 	 */
 	if (static_cpu_has(X86_FEATURE_XSAVES))
-		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;
+		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
+					       xfeatures_mask;
 
 	if (static_cpu_has(X86_FEATURE_FXSR))
 		fpstate_init_fxstate(&state->fxsave);
-- 
1.9.1

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header
  2017-01-24  8:09 ` Ingo Molnar
@ 2017-02-02 20:18   ` Joakim Tjernlund
  0 siblings, 0 replies; 4+ messages in thread
From: Joakim Tjernlund @ 2017-02-02 20:18 UTC (permalink / raw)
  To: mingo, yu-cheng.yu
  Cc: linux-kernel, bp, tglx, dave.hansen, fenghua.yu, x86, hpa, mingo,
	luto, ravi.v.shankar, haokexin

On Tue, 2017-01-24 at 09:09 +0100, Ingo Molnar wrote:
> * Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:

This needs to go to stable too, 4.8 and 4.9

 Jocke

> 
> > The compacted-format XSAVES area is determined at boot time and
> > never changed after.  The field xsave.header.xcomp_bv indicates
> > which components are in the fixed XSAVES format.
> > 
> > In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
> > format since at the time there is no valid data.
> > 
> > However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
> > as in commit: b22cbe404a9cc3c7949e380fa1861e31934c8978, and when
> > __fpu_restore_sig() does fpu__restore() for a COMPAT-mode app,
> > a #GP occurs.  This can be easily triggered by doing valgrind on
> > a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
> > others:
> > 
> > 	https://bugzilla.kernel.org/show_bug.cgi?id=190061
> > 
> > Fix it by setting xcomp_bv correctly.
> > 
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> > Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
> > ---
> >  arch/x86/kernel/fpu/core.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> > index c289e2f..e540dc1 100644
> > --- a/arch/x86/kernel/fpu/core.c
> > +++ b/arch/x86/kernel/fpu/core.c
> > @@ -9,6 +9,7 @@
> >  #include <asm/fpu/regset.h>
> >  #include <asm/fpu/signal.h>
> >  #include <asm/fpu/types.h>
> > +#include <asm/fpu/xstate.h>
> >  #include <asm/traps.h>
> >  
> >  #include <linux/hardirq.h>
> > @@ -235,7 +236,8 @@ void fpstate_init(union fpregs_state *state)
> >  	 * it will #GP. Make sure it is replaced after the memset().
> >  	 */
> >  	if (static_cpu_has(X86_FEATURE_XSAVES))
> > -		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;
> > +		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
> > +					       xfeatures_mask;
> 
> Ok, I have applied this - but it would be cleaner to go one step further and add a 
> fpstate_init_xstate() method that does this in xstate.c and hides the details from 
> arch/x86/kernel/fpu/core.c.
> 
> Similar to how the FX-state initialization is done today:
> 
> >  	if (static_cpu_has(X86_FEATURE_FXSR))
> >  		fpstate_init_fxstate(&state->fxsave);
> 
> Thanks,
> 
> 	Ingo

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header
  2017-01-23 22:54 Yu-cheng Yu
@ 2017-01-24  8:09 ` Ingo Molnar
  2017-02-02 20:18   ` Joakim Tjernlund
  0 siblings, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2017-01-24  8:09 UTC (permalink / raw)
  To: Yu-cheng Yu
  Cc: x86, H. Peter Anvin, Thomas Gleixner, Ingo Molnar, linux-kernel,
	Andy Lutomirski, Borislav Petkov, Dave Hansen, Fenghua Yu,
	Joakim Tjernlund, Ravi V. Shankar, haokexin


* Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:

> The compacted-format XSAVES area is determined at boot time and
> never changed after.  The field xsave.header.xcomp_bv indicates
> which components are in the fixed XSAVES format.
> 
> In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
> format since at the time there is no valid data.
> 
> However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
> as in commit: b22cbe404a9cc3c7949e380fa1861e31934c8978, and when
> __fpu_restore_sig() does fpu__restore() for a COMPAT-mode app,
> a #GP occurs.  This can be easily triggered by doing valgrind on
> a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
> others:
> 
> 	https://bugzilla.kernel.org/show_bug.cgi?id=190061
> 
> Fix it by setting xcomp_bv correctly.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
> ---
>  arch/x86/kernel/fpu/core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index c289e2f..e540dc1 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -9,6 +9,7 @@
>  #include <asm/fpu/regset.h>
>  #include <asm/fpu/signal.h>
>  #include <asm/fpu/types.h>
> +#include <asm/fpu/xstate.h>
>  #include <asm/traps.h>
>  
>  #include <linux/hardirq.h>
> @@ -235,7 +236,8 @@ void fpstate_init(union fpregs_state *state)
>  	 * it will #GP. Make sure it is replaced after the memset().
>  	 */
>  	if (static_cpu_has(X86_FEATURE_XSAVES))
> -		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;
> +		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
> +					       xfeatures_mask;

Ok, I have applied this - but it would be cleaner to go one step further and add a 
fpstate_init_xstate() method that does this in xstate.c and hides the details from 
arch/x86/kernel/fpu/core.c.

Similar to how the FX-state initialization is done today:

>  	if (static_cpu_has(X86_FEATURE_FXSR))
>  		fpstate_init_fxstate(&state->fxsave);

Thanks,

	Ingo

^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header
@ 2017-01-23 22:54 Yu-cheng Yu
  2017-01-24  8:09 ` Ingo Molnar
  0 siblings, 1 reply; 4+ messages in thread
From: Yu-cheng Yu @ 2017-01-23 22:54 UTC (permalink / raw)
  To: x86, H. Peter Anvin, Thomas Gleixner, Ingo Molnar, linux-kernel,
	Andy Lutomirski, Borislav Petkov, Dave Hansen, Fenghua Yu,
	Joakim Tjernlund, Ravi V. Shankar, haokexin
  Cc: Yu-cheng Yu

The compacted-format XSAVES area is determined at boot time and
never changed after.  The field xsave.header.xcomp_bv indicates
which components are in the fixed XSAVES format.

In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
format since at the time there is no valid data.

However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
as in commit: b22cbe404a9cc3c7949e380fa1861e31934c8978, and when
__fpu_restore_sig() does fpu__restore() for a COMPAT-mode app,
a #GP occurs.  This can be easily triggered by doing valgrind on
a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
others:

	https://bugzilla.kernel.org/show_bug.cgi?id=190061

Fix it by setting xcomp_bv correctly.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
---
 arch/x86/kernel/fpu/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index c289e2f..e540dc1 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -9,6 +9,7 @@
 #include <asm/fpu/regset.h>
 #include <asm/fpu/signal.h>
 #include <asm/fpu/types.h>
+#include <asm/fpu/xstate.h>
 #include <asm/traps.h>
 
 #include <linux/hardirq.h>
@@ -235,7 +236,8 @@ void fpstate_init(union fpregs_state *state)
 	 * it will #GP. Make sure it is replaced after the memset().
 	 */
 	if (static_cpu_has(X86_FEATURE_XSAVES))
-		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;
+		state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
+					       xfeatures_mask;
 
 	if (static_cpu_has(X86_FEATURE_FXSR))
 		fpstate_init_fxstate(&state->fxsave);
-- 
1.9.1

^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-02-16 22:20 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2017-02-16 22:14 [PATCH] x86/fpu/xstate: Fix xcomp_bv in XSAVES header Yu-cheng Yu
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2017-01-23 22:54 Yu-cheng Yu
2017-01-24  8:09 ` Ingo Molnar
2017-02-02 20:18   ` Joakim Tjernlund

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