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MdePkg/BasePrintLib: Fix error in Precision position calculation 

Due to a potential hole in the stop condition of loop, the two continuous
access to ArgumentString (index, index+1) inside the loop might cause the
string ending character ('\0') and the byte after it to be read.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
This commit is contained in:
Jian J Wang 2017-12-25 10:07:39 +08:00 committed by Liming Gao
parent c24d664dca
commit 6805854a73
1 changed files with 5 additions and 2 deletions
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7
MdePkg/Library/BasePrintLib/PrintLibInternal.c
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@ -1107,7 +1107,10 @@ BasePrintLibSPrintMarker (
// Compute the number of characters in ArgumentString and store it in Count
// ArgumentString is either null-terminated, or it contains Precision characters
//
for (Count = 0; Count < Precision || ((Flags & PRECISION) == 0); Count++) {
for (Count = 0;
ArgumentString[Count * BytesPerArgumentCharacter] != '\0' &&
(Count < Precision || ((Flags & PRECISION) == 0));
Count++) {
ArgumentCharacter = ((ArgumentString[Count * BytesPerArgumentCharacter] & 0xff) | ((ArgumentString[Count * BytesPerArgumentCharacter + 1]) << 8)) & ArgumentMask;
if (ArgumentCharacter == 0) {
break;
@ -1164,7 +1167,7 @@ BasePrintLibSPrintMarker (
//
// Copy the string into the output buffer performing the required type conversions
//
while (Index < Count) {
while (Index < Count && (*ArgumentString) != '\0') {
ArgumentCharacter = ((*ArgumentString & 0xff) | (((UINT8)*(ArgumentString + 1)) << 8)) & ArgumentMask;
LengthToReturn += (1 * BytesPerOutputCharacter);