[kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->

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* [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs'
@ 2012-09-11 14:31 Fengguang Wu
  2012-09-12  5:58 ` [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r Amos Kong
  0 siblings, 1 reply; 4+ messages in thread
From: Fengguang Wu @ 2012-09-11 14:31 UTC (permalink / raw)
  To: Avi Kivity; +Cc: kernel-janitors, kvm

Hi Avi,

In the kvm/next branch, sparse warns about

arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' 9 <= 15

This is because the array definition is ctxt._regs[NR_VCPU_REGS] where
NR_VCPU_REGS=9 for i386 and 17 for x86_64.

It could be fixed by changing the hard coded 16 to (NR_VCPU_REGS-1).
And I wonder whether you actually want NR_VCPU_REGS here?

Thanks,
Fengguang
---
--- linux-next.orig/arch/x86/kvm/emulate.c	2012-09-11 20:14:00.537475301 +0800
+++ linux-next/arch/x86/kvm/emulate.c	2012-09-11 22:21:57.569227558 +0800
@@ -228,7 +228,7 @@ static void writeback_registers(struct x
 {
 	unsigned reg;
 
-	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, 16)
+	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, NR_VCPU_REGS)
 		ctxt->ops->write_gpr(ctxt, reg, ctxt->_regs[reg]);
 }
 

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r
  2012-09-11 14:31 [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' Fengguang Wu
@ 2012-09-12  5:58 ` Amos Kong
  2012-09-12  6:07   ` Fengguang Wu
  0 siblings, 1 reply; 4+ messages in thread
From: Amos Kong @ 2012-09-12  5:58 UTC (permalink / raw)
  To: Fengguang Wu; +Cc: Avi Kivity, kernel-janitors, kvm

On 11/09/12 22:31, Fengguang Wu wrote:
> Hi Avi,
>
> In the kvm/next branch, sparse warns about
>
> arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' 9 <= 15
>
> This is because the array definition is ctxt._regs[NR_VCPU_REGS] where
> NR_VCPU_REGS=9 for i386 and 17 for x86_64.
>
> It could be fixed by changing the hard coded 16 to (NR_VCPU_REGS-1).

Hi Fengguang,

You replaced 16 to NR_VCPU_REGS in your patch, not (NR_VCPU_REGS-1).
I guess it's a mistake in your commitlog, right?


> And I wonder whether you actually want NR_VCPU_REGS here?
>
> Thanks,
> Fengguang
> ---
> --- linux-next.orig/arch/x86/kvm/emulate.c	2012-09-11 20:14:00.537475301 +0800
> +++ linux-next/arch/x86/kvm/emulate.c	2012-09-11 22:21:57.569227558 +0800
> @@ -228,7 +228,7 @@ static void writeback_registers(struct x
>   {
>   	unsigned reg;
>
> -	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, 16)
> +	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, NR_VCPU_REGS)


>   		ctxt->ops->write_gpr(ctxt, reg, ctxt->_regs[reg]);
>   }
>


-- 
			Amos.

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r
  2012-09-12  5:58 ` [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r Amos Kong
@ 2012-09-12  6:07   ` Fengguang Wu
  2012-09-12  7:37     ` Avi Kivity
  0 siblings, 1 reply; 4+ messages in thread
From: Fengguang Wu @ 2012-09-12  6:07 UTC (permalink / raw)
  To: Amos Kong; +Cc: Avi Kivity, kernel-janitors, kvm

On Wed, Sep 12, 2012 at 01:58:22PM +0800, Amos Kong wrote:
> On 11/09/12 22:31, Fengguang Wu wrote:
> >Hi Avi,
> >
> >In the kvm/next branch, sparse warns about
> >
> >arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' 9 <= 15
> >
> >This is because the array definition is ctxt._regs[NR_VCPU_REGS] where
> >NR_VCPU_REGS=9 for i386 and 17 for x86_64.
> >
> >It could be fixed by changing the hard coded 16 to (NR_VCPU_REGS-1).
> 
> Hi Fengguang,
> 
> You replaced 16 to NR_VCPU_REGS in your patch, not (NR_VCPU_REGS-1).
> I guess it's a mistake in your commitlog, right?

16 = (NR_VCPU_REGS-1). So I mean, if replacing 16 with (NR_VCPU_REGS-1),
there will be no behavior change for the x86_64 case. However I
*suspect* the right value is (NR_VCPU_REGS), as I said in the below
sentence.

> >And I wonder whether you actually want NR_VCPU_REGS here?

For your convenience, here is the relevant code for NR_VCPU_REGS:

        enum kvm_reg {
                VCPU_REGS_RAX = 0,
                VCPU_REGS_RCX = 1,
                VCPU_REGS_RDX = 2,
                VCPU_REGS_RBX = 3,
                VCPU_REGS_RSP = 4,
                VCPU_REGS_RBP = 5,
                VCPU_REGS_RSI = 6,
                VCPU_REGS_RDI = 7,
        #ifdef CONFIG_X86_64
                VCPU_REGS_R8 = 8,
                VCPU_REGS_R9 = 9,
                VCPU_REGS_R10 = 10,
                VCPU_REGS_R11 = 11,
                VCPU_REGS_R12 = 12,
                VCPU_REGS_R13 = 13,
                VCPU_REGS_R14 = 14,
                VCPU_REGS_R15 = 15,
        #endif 
                VCPU_REGS_RIP,
=>             NR_VCPU_REGS
        };

Thanks,
Fengguang

> >--- linux-next.orig/arch/x86/kvm/emulate.c	2012-09-11 20:14:00.537475301 +0800
> >+++ linux-next/arch/x86/kvm/emulate.c	2012-09-11 22:21:57.569227558 +0800
> >@@ -228,7 +228,7 @@ static void writeback_registers(struct x
> >  {
> >  	unsigned reg;
> >
> >-	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, 16)
> >+	for_each_set_bit(reg, (ulong *)&ctxt->regs_dirty, NR_VCPU_REGS)
> 
> 
> >  		ctxt->ops->write_gpr(ctxt, reg, ctxt->_regs[reg]);
> >  }
> >
> 
> 
> -- 
> 			Amos.

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r
  2012-09-12  6:07   ` Fengguang Wu
@ 2012-09-12  7:37     ` Avi Kivity
  0 siblings, 0 replies; 4+ messages in thread
From: Avi Kivity @ 2012-09-12  7:37 UTC (permalink / raw)
  To: Fengguang Wu; +Cc: Amos Kong, kernel-janitors, kvm

On 09/12/2012 09:07 AM, Fengguang Wu wrote:
> On Wed, Sep 12, 2012 at 01:58:22PM +0800, Amos Kong wrote:
>> On 11/09/12 22:31, Fengguang Wu wrote:
>> >Hi Avi,
>> >
>> >In the kvm/next branch, sparse warns about
>> >
>> >arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' 9 <= 15
>> >
>> >This is because the array definition is ctxt._regs[NR_VCPU_REGS] where
>> >NR_VCPU_REGS=9 for i386 and 17 for x86_64.
>> >
>> >It could be fixed by changing the hard coded 16 to (NR_VCPU_REGS-1).
>> 
>> Hi Fengguang,
>> 
>> You replaced 16 to NR_VCPU_REGS in your patch, not (NR_VCPU_REGS-1).
>> I guess it's a mistake in your commitlog, right?
> 
> 16 = (NR_VCPU_REGS-1). So I mean, if replacing 16 with (NR_VCPU_REGS-1),
> there will be no behavior change for the x86_64 case. However I
> *suspect* the right value is (NR_VCPU_REGS), as I said in the below
> sentence.
> 
>> >And I wonder whether you actually want NR_VCPU_REGS here?
> 
> For your convenience, here is the relevant code for NR_VCPU_REGS:
> 
>         enum kvm_reg {
>                 VCPU_REGS_RAX = 0,
>                 VCPU_REGS_RCX = 1,
>                 VCPU_REGS_RDX = 2,
>                 VCPU_REGS_RBX = 3,
>                 VCPU_REGS_RSP = 4,
>                 VCPU_REGS_RBP = 5,
>                 VCPU_REGS_RSI = 6,
>                 VCPU_REGS_RDI = 7,
>         #ifdef CONFIG_X86_64
>                 VCPU_REGS_R8 = 8,
>                 VCPU_REGS_R9 = 9,
>                 VCPU_REGS_R10 = 10,
>                 VCPU_REGS_R11 = 11,
>                 VCPU_REGS_R12 = 12,
>                 VCPU_REGS_R13 = 13,
>                 VCPU_REGS_R14 = 14,
>                 VCPU_REGS_R15 = 15,
>         #endif 
>                 VCPU_REGS_RIP,
> =>             NR_VCPU_REGS
>         };

The right value is NR-1, since the loop excludes RIP.

Note the warning does not point to an actual error, since the high bits
of regs_dirty will be clear on i386.
-- 
error compiling committee.c: too many arguments to function

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2012-09-12  7:37 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2012-09-11 14:31 [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_regs' Fengguang Wu
2012-09-12  5:58 ` [kvm:next 1/1] arch/x86/kvm/emulate.c:232 writeback_registers() error: buffer overflow 'ctxt->_r Amos Kong
2012-09-12  6:07   ` Fengguang Wu
2012-09-12  7:37     ` Avi Kivity

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