From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) (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 D91C721E945F5 for ; Tue, 19 Sep 2017 04:40:54 -0700 (PDT) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Sep 2017 04:43:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,418,1500966000"; d="scan'208";a="1173706478" Received: from shwdeopenpsi014.ccr.corp.intel.com ([10.239.9.13]) by orsmga001.jf.intel.com with ESMTP; 19 Sep 2017 04:43:57 -0700 From: Hao Wu To: edk2-devel@lists.01.org Cc: Hao Wu , Steven Shi , Michael Kinney , Liming Gao Date: Tue, 19 Sep 2017 19:43:47 +0800 Message-Id: <20170919114351.18448-3-hao.a.wu@intel.com> X-Mailer: git-send-email 2.12.0.windows.1 In-Reply-To: <20170919114351.18448-1-hao.a.wu@intel.com> References: <20170919114351.18448-1-hao.a.wu@intel.com> Subject: [PATCH 2/6] MdeModulePkg/PrintLib: Fix possible 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: Tue, 19 Sep 2017 11:40:55 -0000 REF: https://bugzilla.tianocore.org/show_bug.cgi?id=702 Within function InternalPrintLibSPrintMarker(), possible left shift of a negative value is found in: "(*(ArgumentString + 1) << 8)" which involves undefined behavior. Since '*(ArgumentString + 1)' is of type CONST CHAR8 (signed), it will be promoted to type int (signed) during the left shift operation. If '*(ArgumentString + 1)' is a negative value, the behavior will be undefined. 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 explicitly cast '*(ArgumentString + 1)' with UINT8 to resolve this issue. Cc: Steven Shi Cc: Michael Kinney Cc: Liming Gao Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c b/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c index b58db8e011..56534e56c3 100644 --- a/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c +++ b/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c @@ -2108,7 +2108,7 @@ InternalPrintLibSPrintMarker ( // Copy the string into the output buffer performing the required type conversions // while (Index < Count) { - ArgumentCharacter = ((*ArgumentString & 0xff) | (*(ArgumentString + 1) << 8)) & ArgumentMask; + ArgumentCharacter = ((*ArgumentString & 0xff) | (((UINT8)*(ArgumentString + 1)) << 8)) & ArgumentMask; LengthToReturn += (1 * BytesPerOutputCharacter); if ((Flags & COUNT_ONLY_NO_PRINT) == 0 && Buffer != NULL) { -- 2.12.0.windows.1