From: Hao Wu <hao.a.wu@intel.com>
To: edk2-devel@lists.01.org
Cc: Hao Wu <hao.a.wu@intel.com>, Steven Shi <steven.shi@intel.com>,
Michael Kinney <michael.d.kinney@intel.com>
Subject: [PATCH v3 1/5] MdePkg/PrintLib: Fix possible negative value left shift
Date: Thu, 28 Sep 2017 12:32:09 +0800 [thread overview]
Message-ID: <20170928043213.20776-2-hao.a.wu@intel.com> (raw)
In-Reply-To: <20170928043213.20776-1-hao.a.wu@intel.com>
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 <steven.shi@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
---
MdePkg/Library/BasePrintLib/PrintLibInternal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/MdePkg/Library/BasePrintLib/PrintLibInternal.c b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
index cec5b3bc99..28d946472f 100644
--- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
+++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
@@ -1165,7 +1165,7 @@ BasePrintLibSPrintMarker (
// 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
next prev parent reply other threads:[~2017-09-28 4:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-28 4:32 [PATCH v3 0/5] Resolve undefined behaviours in left shift OPs Hao Wu
2017-09-28 4:32 ` Hao Wu [this message]
2017-09-28 4:32 ` [PATCH v3 2/5] MdeModulePkg/PrintLib: Fix possible negative value left shift Hao Wu
2017-09-28 4:32 ` [PATCH v3 3/5] MdeModulePkg/Tpl: Fix " Hao Wu
2017-09-28 4:32 ` [PATCH v3 4/5] MdeModulePkg/DxeNetLib: " Hao Wu
2017-09-28 5:42 ` Wu, Jiaxin
2017-09-28 7:21 ` Fu, Siyuan
2017-09-28 7:30 ` Ye, Ting
2017-09-28 4:32 ` [PATCH v3 5/5] MdeModulePkg/AtaAtapiPassThru: Fix possible out of range " Hao Wu
2017-09-28 5:12 ` Zeng, Star
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