fpu.state is allocated from task_xstate_cachep, the size of
task_xstate_cachep is xstate_size. But fpu.state is an union
struct, which size is bigger than xstate_size if cpu_has_xsave,
so if we want to visit fpu.state->xsave, the memory we allocated
for fpu.state is not enough.
This caused many poison/redzone overwritten alerts on task_xstate while using kvm.
[ 1899.399373] =============================================================================
[ 1899.399377] BUG task_xstate: Poison overwritten
[ 1899.399378] -----------------------------------------------------------------------------
[ 1899.399379]
[ 1899.399382] INFO: 0xffff88020aca2100-0xffff88020aca217f. First byte 0x0 instead of 0x6b
[ 1899.399385] INFO: Slab 0xffffea000725c300 objects=23 used=12 fp=0xffff88020aca2100 flags=0x200000000040c1
[ 1899.399387] INFO: Object 0xffff88020aca2100 @offset=8448 fp=0xffff88020aca23c0
With this patch applied, the poison overwritten alert disappeared.
Signed-off-by: Xiaotian Feng <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Avi Kivity <[email protected]>
Cc: Peter Zijlstra <[email protected]>
---
arch/x86/kernel/process.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index d401f1d..609bee5 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -59,7 +59,7 @@ void free_thread_info(struct thread_info *ti)
void arch_task_cache_init(void)
{
task_xstate_cachep =
- kmem_cache_create("task_xstate", xstate_size,
+ kmem_cache_create("task_xstate", sizeof(union thread_xstate),
__alignof__(union thread_xstate),
SLAB_PANIC | SLAB_NOTRACK, NULL);
}
--
1.7.2.1
On Thu, Aug 12, 2010 at 6:45 AM, Xiaotian Feng <[email protected]> wrote:
> fpu.state is allocated from task_xstate_cachep, the size of
> task_xstate_cachep is xstate_size. But fpu.state is an union
> struct, which size is bigger than xstate_size if cpu_has_xsave,
> so if we want to visit fpu.state->xsave, the memory we allocated
> for fpu.state is not enough.
>
> This caused many poison/redzone overwritten alerts on task_xstate while using kvm.
>
> [ 1899.399373] =============================================================================
> [ 1899.399377] BUG task_xstate: Poison overwritten
> [ 1899.399378] -----------------------------------------------------------------------------
> [ 1899.399379]
> [ 1899.399382] INFO: 0xffff88020aca2100-0xffff88020aca217f. First byte 0x0 instead of 0x6b
> [ 1899.399385] INFO: Slab 0xffffea000725c300 objects=23 used=12 fp=0xffff88020aca2100 flags=0x200000000040c1
> [ 1899.399387] INFO: Object 0xffff88020aca2100 @offset=8448 fp=0xffff88020aca23c0
>
> With this patch applied, the poison overwritten alert disappeared.
>
> Signed-off-by: Xiaotian Feng <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Brian Gerst <[email protected]>
> Cc: Avi Kivity <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> ---
> arch/x86/kernel/process.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index d401f1d..609bee5 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -59,7 +59,7 @@ void free_thread_info(struct thread_info *ti)
> void arch_task_cache_init(void)
> {
> task_xstate_cachep =
> - kmem_cache_create("task_xstate", xstate_size,
> + kmem_cache_create("task_xstate", sizeof(union thread_xstate),
> __alignof__(union thread_xstate),
> SLAB_PANIC | SLAB_NOTRACK, NULL);
> }
This isn't the right solution. The point of having a variable
xstate_size is to only allocate the memory that is needed for the
capabilities of the cpu. The real bug is that some code is trying to
use xsave_struct when it either shouldn't be (because the cpu doesn't
support xsave), or because xstate_size < sizeof(xsave_struct).
Looking at xstate_enable_boot_cpu(), the xstate_size is set from
cpuid. It's possible that it is smaller than sizeof(xsave_strruct).
Maybe a sanity check should be added there?
--
Brian Gerst
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 <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Suresh Siddha <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Avi Kivity <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Sheng Yang <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Gleb Natapov <[email protected]>
Cc: Jan Kiszka <[email protected]>
---
arch/x86/kernel/i387.c | 1 +
arch/x86/kvm/x86.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 1f11f5c..a46cb35 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -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;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 25f1907..3a09c62 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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,
@@ -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;
--
1.7.2.1
On Friday 13 August 2010 15:19:11 Xiaotian Feng wrote:
> 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 <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Suresh Siddha <[email protected]>
> Cc: Brian Gerst <[email protected]>
> Cc: Avi Kivity <[email protected]>
> Cc: Robert Richter <[email protected]>
> Cc: Sheng Yang <[email protected]>
> Cc: Marcelo Tosatti <[email protected]>
> Cc: Gleb Natapov <[email protected]>
> Cc: Jan Kiszka <[email protected]>
Reviewed-by: Sheng Yang <[email protected]>
--
regards
Yang, Sheng
> ---
> arch/x86/kernel/i387.c | 1 +
> arch/x86/kvm/x86.c | 4 ++--
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
> index 1f11f5c..a46cb35 100644
> --- a/arch/x86/kernel/i387.c
> +++ b/arch/x86/kernel/i387.c
> @@ -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;
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 25f1907..3a09c62 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -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,
> @@ -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;
Avi, do you want to take this one or should I?
-hpa
On 08/13/2010 12:19 AM, Xiaotian Feng wrote:
> 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 <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Suresh Siddha <[email protected]>
> Cc: Brian Gerst <[email protected]>
> Cc: Avi Kivity <[email protected]>
> Cc: Robert Richter <[email protected]>
> Cc: Sheng Yang <[email protected]>
> Cc: Marcelo Tosatti <[email protected]>
> Cc: Gleb Natapov <[email protected]>
> Cc: Jan Kiszka <[email protected]>
> ---
> arch/x86/kernel/i387.c | 1 +
> arch/x86/kvm/x86.c | 4 ++--
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
> index 1f11f5c..a46cb35 100644
> --- a/arch/x86/kernel/i387.c
> +++ b/arch/x86/kernel/i387.c
> @@ -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;
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 25f1907..3a09c62 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -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,
> @@ -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;
On 08/13/2010 10:19 AM, Xiaotian Feng wrote:
> 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.
Thanks, applied.
--
error compiling committee.c: too many arguments to function
On 08/14/2010 12:03 AM, H. Peter Anvin wrote:
> Avi, do you want to take this one or should I?
I will, thanks.
--
error compiling committee.c: too many arguments to function
Feel free to add my ack.
"Avi Kivity" <[email protected]> wrote:
> On 08/14/2010 12:03 AM, H. Peter Anvin wrote:
>> Avi, do you want to take this one or should I?
>
>I will, thanks.
>
>--
>error compiling committee.c: too many arguments to function
>
--
Sent from my mobile phone. Please pardon any lack of formatting.