* [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
* [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
* 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
* 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
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