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 2/2] MdeModulePkg/PrintLib: Avoid reading content beyond the format string
Date: Tue, 23 May 2017 09:19:25 +0800 [thread overview]
Message-ID: <20170523011925.6264-3-hao.a.wu@intel.com> (raw)
In-Reply-To: <20170523011925.6264-1-hao.a.wu@intel.com>
In functions DxePrintLibPrint2ProtocolVaListToBaseList() and
InternalPrintLibSPrintMarker(), 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>
---
MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c | 66 ++++++++++++++++----
1 file changed, 55 insertions(+), 11 deletions(-)
diff --git a/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c b/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c
index 9f702c4fef..342eee42fc 100644
--- a/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c
+++ b/MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c
@@ -130,7 +130,11 @@ DxePrintLibPrint2ProtocolVaListToBaseList (
//
// Get the first character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
while (FormatCharacter != 0) {
if (FormatCharacter == '%') {
@@ -148,7 +152,11 @@ DxePrintLibPrint2ProtocolVaListToBaseList (
//
// Get the next character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
switch (FormatCharacter) {
case '.':
@@ -239,7 +247,11 @@ DxePrintLibPrint2ProtocolVaListToBaseList (
//
// Get the next character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
}
return TRUE;
}
@@ -1596,7 +1608,11 @@ InternalPrintLibSPrintMarker (
//
// Get the first character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
//
// Loop until the end of the format string is reached or the output buffer is full
@@ -1628,7 +1644,11 @@ InternalPrintLibSPrintMarker (
//
for (Done = FALSE; !Done; ) {
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
switch (FormatCharacter) {
case '.':
Flags |= PRECISION;
@@ -1681,7 +1701,11 @@ InternalPrintLibSPrintMarker (
for (Count = 0; ((FormatCharacter >= '0') && (FormatCharacter <= '9')); ){
Count = (Count * 10) + FormatCharacter - '0';
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
}
Format -= BytesPerFormatCharacter;
if ((Flags & PRECISION) == 0) {
@@ -1960,7 +1984,11 @@ InternalPrintLibSPrintMarker (
case '\r':
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
if (FormatCharacter == '\n') {
//
// Translate '\r\n' to '\r\n'
@@ -1981,7 +2009,11 @@ InternalPrintLibSPrintMarker (
//
ArgumentString = "\r\n";
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
if (FormatCharacter != '\r') {
Format -= BytesPerFormatCharacter;
}
@@ -2000,7 +2032,11 @@ InternalPrintLibSPrintMarker (
case '\r':
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
if (FormatCharacter == '\n') {
//
// Translate '\r\n' to '\r\n'
@@ -2021,7 +2057,11 @@ InternalPrintLibSPrintMarker (
//
ArgumentString = "\r\n";
Format += BytesPerFormatCharacter;
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
if (FormatCharacter != '\r') {
Format -= BytesPerFormatCharacter;
}
@@ -2149,7 +2189,11 @@ InternalPrintLibSPrintMarker (
//
// Get the next character from the format string
//
- FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ if (BytesPerFormatCharacter == 1) {
+ FormatCharacter = (*Format & 0xff) & FormatMask;
+ } else {
+ FormatCharacter = ((*Format & 0xff) | (*(Format + 1) << 8)) & FormatMask;
+ }
}
if ((Flags & COUNT_ONLY_NO_PRINT) != 0) {
--
2.12.0.windows.1
prev parent reply other threads:[~2017-05-23 1:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-23 1:19 [PATCH 0/2] Avoid reading undefined contents Hao Wu
2017-05-23 1:19 ` [PATCH 1/2] MdePkg/BasePrintLib: Avoid reading content beyond the format string Hao Wu
2017-05-23 1:19 ` Hao Wu [this message]
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