linux-kernel - Re: [patch v2] x86, UV: integer wrap bug in uv_hub_ipi

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Date:	Sun, 02 Dec 2012 16:33:59 +0100
From:	walter harms <wharms@....de>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Russ Anderson <rja@....com>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch v2] x86, UV: integer wrap bug in uv_hub_ipi_value()



Am 02.12.2012 11:44, schrieb Dan Carpenter:
> This is a static checker fix.  The problem is that we store the bits
> from "uv_apicid_hibits" into "apicid" (the high 16 bits) but then we
> shift it 16 bit to the left.  "apicid" is an int so it wraps and we lose
> them.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> v2: Style fix.  Don't use ulong.
> 
> I don't have this hardware so I can't test it.  There may also be other
> bugs which this patch does not addressed.  These files are only compiled
> on x86_64 and "unsigned long" is used throughout to mean 64 bits.
> 
> diff --git a/arch/x86/include/asm/uv/uv_hub.h b/arch/x86/include/asm/uv/uv_hub.h
> index 21f7385..e7a83d5 100644
> --- a/arch/x86/include/asm/uv/uv_hub.h
> +++ b/arch/x86/include/asm/uv/uv_hub.h
> @@ -577,7 +577,7 @@ static unsigned long uv_hub_ipi_value(int apicid, int vector, int mode)
>  {
>  	apicid |= uv_apicid_hibits;
>  	return (1UL << UVH_IPI_INT_SEND_SHFT) |
> -			((apicid) << UVH_IPI_INT_APIC_ID_SHFT) |
> +			((unsigned long)apicid << UVH_IPI_INT_APIC_ID_SHFT) |
>  			(mode << UVH_IPI_INT_DELIVERY_MODE_SHFT) |
>  			(vector << UVH_IPI_INT_VECTOR_SHFT);
>  }
> diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
> index 8cfade9..6d93b2f 100644
> --- a/arch/x86/kernel/apic/x2apic_uv_x.c
> +++ b/arch/x86/kernel/apic/x2apic_uv_x.c
> @@ -194,13 +194,13 @@ static int __cpuinit uv_wakeup_secondary(int phys_apicid, unsigned long start_ri
>  	pnode = uv_apicid_to_pnode(phys_apicid);
>  	phys_apicid |= uv_apicid_hibits;
>  	val = (1UL << UVH_IPI_INT_SEND_SHFT) |
> -	    (phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
> +	    ((unsigned long)phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
>  	    ((start_rip << UVH_IPI_INT_VECTOR_SHFT) >> 12) |
>  	    APIC_DM_INIT;
>  	uv_write_global_mmr64(pnode, UVH_IPI_INT, val);
>  
>  	val = (1UL << UVH_IPI_INT_SEND_SHFT) |
> -	    (phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
> +	    ((unsigned long)phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
>  	    ((start_rip << UVH_IPI_INT_VECTOR_SHFT) >> 12) |
>  	    APIC_DM_STARTUP;
>  	uv_write_global_mmr64(pnode, UVH_IPI_INT, val);

making this more readable is hard but what is about:

val=(1UL << UVH_IPI_INT_SEND_SHFT) |
     ((unsigned long)phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
      ((start_rip << UVH_IPI_INT_VECTOR_SHFT) >> 12);

 uv_write_global_mmr64(pnode, UVH_IPI_INT, val|APIC_DM_INIT);

 uv_write_global_mmr64(pnode, UVH_IPI_INT, val|APIC_DM_STARTUP);


just my 2 cents,
 re
  wh

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