* [PATCH] x86/xsaves: get_xsave_addr needs check the xsave header
@ 2015-12-18 10:50 Huaitong Han
2015-12-18 11:13 ` Andrew Cooper
0 siblings, 1 reply; 2+ messages in thread
From: Huaitong Han @ 2015-12-18 10:50 UTC (permalink / raw)
To: jbeulich, andrew.cooper3, keir; +Cc: Huaitong Han, shuai.ruan, xen-devel
The check needs to be against the xsave header in the area, rather than
Xen's maximum xfeature_mask. A guest might easily have a smaller xcr0
than the maximum Xen is willing to allow, causing the pointer below to
be bogus.
Signed-off-by: Huaitong Han <huaitong.han@intel.com>
---
xen/arch/x86/xstate.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index b65da38..d87ab40 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -146,12 +146,13 @@ static void __init setup_xstate_comp(void)
}
}
-static void *get_xsave_addr(void *xsave, unsigned int xfeature_idx)
+static void *get_xsave_addr(struct xsave_struct *xsave,
+ unsigned int xfeature_idx)
{
- if ( !((1ul << xfeature_idx) & xfeature_mask) )
+ if ( !((1ul << xfeature_idx) & xsave->xsave_hdr.xstate_bv) )
return NULL;
- return xsave + xstate_comp_offsets[xfeature_idx];
+ return (void *)xsave + xstate_comp_offsets[xfeature_idx];
}
void expand_xsave_states(struct vcpu *v, void *dest, unsigned int size)
--
2.4.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] x86/xsaves: get_xsave_addr needs check the xsave header
2015-12-18 10:50 [PATCH] x86/xsaves: get_xsave_addr needs check the xsave header Huaitong Han
@ 2015-12-18 11:13 ` Andrew Cooper
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Cooper @ 2015-12-18 11:13 UTC (permalink / raw)
To: Huaitong Han, jbeulich, keir; +Cc: shuai.ruan, xen-devel
On 18/12/15 10:50, Huaitong Han wrote:
> The check needs to be against the xsave header in the area, rather than
> Xen's maximum xfeature_mask. A guest might easily have a smaller xcr0
> than the maximum Xen is willing to allow, causing the pointer below to
> be bogus.
>
> Signed-off-by: Huaitong Han <huaitong.han@intel.com>
> ---
> xen/arch/x86/xstate.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
> index b65da38..d87ab40 100644
> --- a/xen/arch/x86/xstate.c
> +++ b/xen/arch/x86/xstate.c
> @@ -146,12 +146,13 @@ static void __init setup_xstate_comp(void)
> }
> }
>
> -static void *get_xsave_addr(void *xsave, unsigned int xfeature_idx)
> +static void *get_xsave_addr(struct xsave_struct *xsave,
> + unsigned int xfeature_idx)
> {
> - if ( !((1ul << xfeature_idx) & xfeature_mask) )
> + if ( !((1ul << xfeature_idx) & xsave->xsave_hdr.xstate_bv) )
> return NULL;
>
> - return xsave + xstate_comp_offsets[xfeature_idx];
> + return (void *)xsave + xstate_comp_offsets[xfeature_idx];
This indeed fixes one of the issues. However, you must also check
xcomb_bv & XSTATE_COMPACTION_ENABLED before using xstate_comp_offsets.
I think you should end up with something like:
if ( xsave->xsave_hdr.xcomb_bv & XSTATE_COMPACTION_ENABLED )
return (void *)xsave + xstate_comp_offsets[xfeature_idx];
else
return (void *)xsave + xstate_offsets[xfeature_idx];
which allows get_xsave_addr() to work on both compressed and
uncompressed xstate areas.
~Andrew
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2015-12-18 11:13 ` Andrew Cooper
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