From: Hao Wu <hao.a.wu@intel.com>
To: edk2-devel@lists.01.org
Cc: Hao Wu <hao.a.wu@intel.com>, Jiewen Yao <jiewen.yao@intel.com>,
Liming Gao <liming.gao@intel.com>,
Michael Kinney <michael.d.kinney@intel.com>
Subject: [PATCH v2 1/2] MdePkg/BasePrintLib: Avoid reading content beyond the format string
Date: Wed, 31 May 2017 14:13:18 +0800 [thread overview]
Message-ID: <20170531061319.21976-2-hao.a.wu@intel.com> (raw)
In-Reply-To: <20170531061319.21976-1-hao.a.wu@intel.com>
https://bugzilla.tianocore.org/show_bug.cgi?id=567
In function BasePrintLibSPrintMarker(), when processing ASCII format
strings, if the format string walker pointer 'Format' is pointing at the
end of the format string (i.e. '\0'), the following expression:
*(Format + 1)
will read an undefined value.
Though this value won't affect the functionality, since it will be masked
by variable 'FormatMask':
(*(Format + 1) << 8)) & FormatMask
(FormatMask is 0xff for ASCII format string)
This commit adds additional logic to avoid reading undefined content.
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
MdePkg/Library/BasePrintLib/PrintLibInternal.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/MdePkg/Library/BasePrintLib/PrintLibInternal.c b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
index 9b15a07ac0..cec5b3bc99 100644
--- a/MdePkg/Library/BasePrintLib/PrintLibInternal.c
+++ b/MdePkg/Library/BasePrintLib/PrintLibInternal.c
@@ -653,7 +653,7 @@ BasePrintLibSPrintMarker (
//
// Get the first character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
//
// Loop until the end of the format string is reached or the output buffer is full
@@ -685,7 +685,7 @@ BasePrintLibSPrintMarker (
//
for (Done = FALSE; !Done; ) {
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
switch (FormatCharacter) {
case '.':
Flags |= PRECISION;
@@ -738,7 +738,7 @@ BasePrintLibSPrintMarker (
for (Count = 0; ((FormatCharacter >= '0') && (FormatCharacter <= '9')); ){
Count = (Count * 10) + FormatCharacter - '0';
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
}
Format -= BytesPerFormatCharacter;
if ((Flags & PRECISION) == 0) {
@@ -1017,7 +1017,7 @@ BasePrintLibSPrintMarker (
case '\r':
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
if (FormatCharacter == '\n') {
//
// Translate '\r\n' to '\r\n'
@@ -1038,7 +1038,7 @@ BasePrintLibSPrintMarker (
//
ArgumentString = "\r\n";
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
if (FormatCharacter != '\r') {
Format -= BytesPerFormatCharacter;
}
@@ -1057,7 +1057,7 @@ BasePrintLibSPrintMarker (
case '\r':
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
if (FormatCharacter == '\n') {
//
// Translate '\r\n' to '\r\n'
@@ -1078,7 +1078,7 @@ BasePrintLibSPrintMarker (
//
ArgumentString = "\r\n";
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
if (FormatCharacter != '\r') {
Format -= BytesPerFormatCharacter;
}
@@ -1206,7 +1206,7 @@ BasePrintLibSPrintMarker (
//
// Get the next character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ FormatCharacter = ((*Format & 0xff) | ((BytesPerFormatCharacter == 1) ? 0 : (*(Format + 1) << 8))) & FormatMask;
}
if ((Flags & COUNT_ONLY_NO_PRINT) != 0) {
--
2.12.0.windows.1
next prev parent reply other threads:[~2017-05-31 6:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-31 6:13 [PATCH v2 0/2] Avoid reading undefined contents in PrintLib Hao Wu
2017-05-31 6:13 ` Hao Wu [this message]
2017-05-31 6:13 ` [PATCH v2 2/2] MdeModulePkg/PrintLib: Avoid reading content beyond the format string Hao Wu
2017-05-31 7:05 ` [PATCH v2 0/2] Avoid reading undefined contents in PrintLib Gao, Liming
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