From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=192.55.52.115; helo=mga14.intel.com; envelope-from=jiaxin.wu@intel.com; receiver=edk2-devel@lists.01.org Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) (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 B968A21EC8D17 for ; Wed, 27 Sep 2017 22:39:24 -0700 (PDT) Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Sep 2017 22:42:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,448,1500966000"; d="scan'208";a="156425700" Received: from fmsmsx105.amr.corp.intel.com ([10.18.124.203]) by fmsmga005.fm.intel.com with ESMTP; 27 Sep 2017 22:42:38 -0700 Received: from fmsmsx156.amr.corp.intel.com (10.18.116.74) by FMSMSX105.amr.corp.intel.com (10.18.124.203) with Microsoft SMTP Server (TLS) id 14.3.319.2; Wed, 27 Sep 2017 22:42:38 -0700 Received: from shsmsx151.ccr.corp.intel.com (10.239.6.50) by fmsmsx156.amr.corp.intel.com (10.18.116.74) with Microsoft SMTP Server (TLS) id 14.3.319.2; Wed, 27 Sep 2017 22:42:37 -0700 Received: from shsmsx103.ccr.corp.intel.com ([169.254.4.213]) by SHSMSX151.ccr.corp.intel.com ([169.254.3.98]) with mapi id 14.03.0319.002; Thu, 28 Sep 2017 13:42:35 +0800 From: "Wu, Jiaxin" To: "Wu, Hao A" , "edk2-devel@lists.01.org" CC: "Shi, Steven" , "Fu, Siyuan" , "Ye, Ting" , "Long, Qin" , "Zeng, Star" , "Dong, Eric" , "Paolo Bonzini" Thread-Topic: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift Thread-Index: AQHTOBLU2RToY2KQw0WEC6ebOSN/RaLJyP5w Date: Thu, 28 Sep 2017 05:42:35 +0000 Message-ID: <895558F6EA4E3B41AC93A00D163B72741633A5A3@SHSMSX103.ccr.corp.intel.com> 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: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiN2Y5NDZhMDQtOTJhOS00ODhlLTljMzMtZWY4MjQxNDEyNWNmIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE2LjUuOS4zIiwiVHJ1c3RlZExhYmVsSGFzaCI6IjBQR2dIQlwvMEczUWlhR3NyY2dDcm5kc2FTMmJwRWRpSks0alZTZFNaNlBFPSJ9 x-ctpclassification: CTP_IC dlp-product: dlpe-windows dlp-version: 11.0.0.116 dlp-reaction: no-action 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 05:39:24 -0000 Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Reviewed-by: Wu Jiaxin > -----Original Message----- > From: Wu, Hao A > 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, Jiaxi= n > ; Long, Qin ; Zeng, Star > ; Dong, Eric ; Paolo Bonzini > > Subject: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left > shift >=20 > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3D698 >=20 > Within function NetRandomInitSeed(), left shift a negative value is used > in: > "~Time.Hour << 24" >=20 > which involves undefined behavior. >=20 > Since Time.Hour is of type UINT8 (range from 0 to 23), hence ~Time.Hour > will be a negative value (of type int, signed). >=20 > 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. >=20 > This commit will remove the '~' operator before 'Time.Hour', since it > seems like an implementation choice for generating the seed. >=20 > 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(-) >=20 > diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c > b/MdeModulePkg/Library/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.Second); > + Seed =3D (Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | > Time.Second); > Seed ^=3D Time.Nanosecond; > Seed ^=3D Time.Year << 7; >=20 > -- > 2.12.0.windows.1