From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.65; helo=mga03.intel.com; envelope-from=ting.ye@intel.com; receiver=edk2-devel@lists.01.org Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 3673B20945BA4 for ; Thu, 28 Sep 2017 00:27:05 -0700 (PDT) Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Sep 2017 00:30:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,449,1500966000"; d="scan'208";a="156456144" Received: from fmsmsx108.amr.corp.intel.com ([10.18.124.206]) by fmsmga005.fm.intel.com with ESMTP; 28 Sep 2017 00:30:12 -0700 Received: from fmsmsx119.amr.corp.intel.com (10.18.124.207) by FMSMSX108.amr.corp.intel.com (10.18.124.206) with Microsoft SMTP Server (TLS) id 14.3.319.2; Thu, 28 Sep 2017 00:30:12 -0700 Received: from shsmsx102.ccr.corp.intel.com (10.239.4.154) by FMSMSX119.amr.corp.intel.com (10.18.124.207) with Microsoft SMTP Server (TLS) id 14.3.319.2; Thu, 28 Sep 2017 00:30:11 -0700 Received: from shsmsx103.ccr.corp.intel.com ([169.254.4.213]) by shsmsx102.ccr.corp.intel.com ([169.254.2.175]) with mapi id 14.03.0319.002; Thu, 28 Sep 2017 15:30:10 +0800 From: "Ye, Ting" To: "Wu, Hao A" , "edk2-devel@lists.01.org" CC: "Shi, Steven" , "Fu, Siyuan" , "Wu, Jiaxin" , "Long, Qin" , "Zeng, Star" , "Dong, Eric" , "Paolo Bonzini" Thread-Topic: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift Thread-Index: AQHTOBLUuBd9U8kVAky8/v16JvvLGaLJ5wSw Date: Thu, 28 Sep 2017 07:30:09 +0000 Message-ID: References: <20170928043213.20776-1-hao.a.wu@intel.com> <20170928043213.20776-5-hao.a.wu@intel.com> In-Reply-To: <20170928043213.20776-5-hao.a.wu@intel.com> Accept-Language: zh-CN, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] MIME-Version: 1.0 Subject: Re: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Sep 2017 07:27:06 -0000 Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Reviewed-by: Ye Ting =20 -----Original Message----- From: Wu, Hao A=20 Sent: Thursday, September 28, 2017 12:32 PM To: edk2-devel@lists.01.org Cc: Wu, Hao A ; Shi, Steven ; Fu,= Siyuan ; Ye, Ting ; Wu, Jiaxin ; Long, Qin ; Zeng, Star ; Dong, Eric ; Paolo Bonzini Subject: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shi= ft REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3D698 Within function NetRandomInitSeed(), left shift a negative value is used in: "~Time.Hour << 24" which involves undefined behavior. Since Time.Hour is of type UINT8 (range from 0 to 23), hence ~Time.Hour wil= l be a negative value (of type int, signed). According to the C11 spec, Section 6.5.7: > 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated > bits are filled with zeros. If E1 has an unsigned type, the value > of the result is E1 * 2^E2 , reduced modulo one more than the > maximum value representable in the result type. If E1 has a signed > type and nonnegative value, and E1 * 2^E2 is representable in the > result type, then that is the resulting value; otherwise, the > behavior is undefined. This commit will remove the '~' operator before 'Time.Hour', since it seems= like an implementation choice for generating the seed. Cc: Steven Shi Cc: Fu Siyuan Cc: Ye Ting Cc: Wu Jiaxin Cc: Qin Long Cc: Star Zeng Cc: Eric Dong Cc: Paolo Bonzini Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- MdeModulePkg/Library/DxeNetLib/DxeNetLib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c b/MdeModulePkg/Libr= ary/DxeNetLib/DxeNetLib.c index 7cd7e3aca0..1ee77fe036 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64 MonotonicCount; =20 gRT->GetTime (&Time, NULL); - Seed =3D (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Se= cond); + Seed =3D (Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 |=20 + Time.Second); Seed ^=3D Time.Nanosecond; Seed ^=3D Time.Year << 7; =20 -- 2.12.0.windows.1