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....@intel.com>
Cc: Michael Kinney <michael.d.kin...@intel.com>
Cc: Liming Gao <liming....@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a...@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
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