From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) (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 00EDD21E1B742 for ; Wed, 20 Sep 2017 23:43:20 -0700 (PDT) Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Sep 2017 23:46:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,424,1500966000"; d="scan'208";a="154331035" Received: from shwdeopenpsi014.ccr.corp.intel.com ([10.239.9.13]) by fmsmga006.fm.intel.com with ESMTP; 20 Sep 2017 23:46:25 -0700 From: Hao Wu To: edk2-devel@lists.01.org Cc: Hao Wu , Steven Shi , Fu Siyuan , Ye Ting , Wu Jiaxin , Qin Long , Star Zeng , Eric Dong , Paolo Bonzini Date: Thu, 21 Sep 2017 14:46:15 +0800 Message-Id: <20170921064617.2628-5-hao.a.wu@intel.com> X-Mailer: git-send-email 2.12.0.windows.1 In-Reply-To: <20170921064617.2628-1-hao.a.wu@intel.com> References: <20170921064617.2628-1-hao.a.wu@intel.com> Subject: [PATCH v2 4/6] 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, 21 Sep 2017 06:43:21 -0000 REF: https://bugzilla.tianocore.org/show_bug.cgi?id=698 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 will 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/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; gRT->GetTime (&Time, NULL); - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); + Seed = (Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); Seed ^= Time.Nanosecond; Seed ^= Time.Year << 7; -- 2.12.0.windows.1