Re: [Patch] MdeModulePkg/DxeNetLib: Add array range check in NetIp6IsNetEqual().

["Wang, Fan" <fan.wang@intel.com>]

Thanks, Jiaxin, I will revise it.

Best Regards
Fan

-----Original Message-----
From: Wu, Jiaxin 
Sent: Thursday, January 11, 2018 3:48 PM
To: Wang, Fan <fan.wang@intel.com>; edk2-devel@lists.01.org
Cc: Fu, Siyuan <siyuan.fu@intel.com>; Wu, Hao A <hao.a.wu@intel.com>
Subject: RE: [Patch] MdeModulePkg/DxeNetLib: Add array range check in NetIp6IsNetEqual().

Hi Fan,

I think we need to update the below ASSERT if apply you patch:

	ASSERT ((Ip1 != NULL) && (Ip2 != NULL) && (PrefixLength <= IP6_PREFIX_MAX));

Update To: 

	ASSERT ((Ip1 != NULL) && (Ip2 != NULL) && (PrefixLength < IP6_PREFIX_MAX));


If PrefixLength is IP6_PREFIX_MAX(128), then the Byte can be 16:

	Byte = (UINT8) (PrefixLength / 8);

So, it will conflict with your patch ASSERT:

	ASSERT (Byte < 16);

Thanks,
Jiaxin

> -----Original Message-----
> From: Wang, Fan
> Sent: Thursday, January 11, 2018 10:39 AM
> To: edk2-devel@lists.01.org
> Cc: Fu, Siyuan <siyuan.fu@intel.com>; Wu, Jiaxin 
> <jiaxin.wu@intel.com>; Wu, Hao A <hao.a.wu@intel.com>
> Subject: [Patch] MdeModulePkg/DxeNetLib: Add array range check in 
> NetIp6IsNetEqual().
> 
> * The library API use array elements without any index range check, this
>   patch is to fix this issue to avoid null pointer reference.
> 
> Cc: Fu Siyuan <siyuan.fu@intel.com>
> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> Cc: Hao Wu <hao.a.wu@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Wang Fan <fan.wang@intel.com>
> ---
>  MdeModulePkg/Library/DxeNetLib/DxeNetLib.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> index cbce28f..34e11a8 100644
> --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> @@ -840,10 +840,14 @@ NetIp6IsNetEqual (
>    }
> 
>    if (Bit > 0) {
>      Mask = (UINT8) (0xFF << (8 - Bit));
> 
> +    ASSERT (Byte < 16);
> +    if (Byte >= 16) {
> +      return FALSE;
> +    }
>      if ((Ip1->Addr[Byte] & Mask) != (Ip2->Addr[Byte] & Mask)) {
>        return FALSE;
>      }
>    }
> 
> --
> 1.9.5.msysgit.1