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KVM: fix poison overwritten caused by using wrong xstate size
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fpu.state is allocated from task_xstate_cachep, the size of task_xstate_cachep
is xstate_size. xstate_size is set from cpuid instruction, which is often
smaller than sizeof(struct xsave_struct). kvm is using sizeof(struct xsave_struct)
to fill in/out fpu.state.xsave, as what we allocated for fpu.state is
xstate_size, kernel will write out of memory and caused poison/redzone/padding
overwritten warnings.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Reviewed-by: Sheng Yang <sheng@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Sheng Yang <sheng@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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Xiaotian Feng authored and Avi Kivity committed Aug 15, 2010
1 parent 3cfc2c4 commit f45755b
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Showing 2 changed files with 3 additions and 2 deletions.
1 change: 1 addition & 0 deletions arch/x86/kernel/i387.c
Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@

static unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
EXPORT_SYMBOL_GPL(xstate_size);
unsigned int sig_xstate_ia32_size = sizeof(struct _fpstate_ia32);
static struct i387_fxsave_struct fx_scratch __cpuinitdata;

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4 changes: 2 additions & 2 deletions arch/x86/kvm/x86.c
Original file line number Diff line number Diff line change
Expand Up @@ -2387,7 +2387,7 @@ static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
if (cpu_has_xsave)
memcpy(guest_xsave->region,
&vcpu->arch.guest_fpu.state->xsave,
sizeof(struct xsave_struct));
xstate_size);
else {
memcpy(guest_xsave->region,
&vcpu->arch.guest_fpu.state->fxsave,
Expand All @@ -2405,7 +2405,7 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,

if (cpu_has_xsave)
memcpy(&vcpu->arch.guest_fpu.state->xsave,
guest_xsave->region, sizeof(struct xsave_struct));
guest_xsave->region, xstate_size);
else {
if (xstate_bv & ~XSTATE_FPSSE)
return -EINVAL;
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