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MdePkg/SafeString: Fix potential out-of-bound memory access 

Today's implementation of [Ascii]StrnCpyS/[Ascii]StrnCatS calls
StrnLenS () to get the length of source string but supplies the
destination buffer size as max size.
It's a bug that may cause out-of-bound memory access.
For example:
  StrnCpyS (Dest[10], 10, "hello", 6)
  -> StrnLenS ("hello", 10) //< cause out-of bound memory access

In a pool guard enabled environment, when using shell to edit an
existing file which contains empty line, the page fault is met.

The patch fixes the four library functions to avoid such
out-of-bound memory access.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
This commit is contained in:
Ruiyu Ni 2018-02-02 18:47:18 +08:00
parent 7162fdb037
commit 56658c22a6
1 changed files with 9 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
MdePkg/Library/BaseLib/SafeString.c
View File

@ -1,7 +1,7 @@
/** @file
Safe String functions.
Copyright (c) 2014 - 2017, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2014 - 2018, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
@ -342,7 +342,7 @@ StrnCpyS (
//
// 4. If Length is not less than DestMax, then DestMax shall be greater than StrnLenS(Source, DestMax).
//
SourceLen = StrnLenS (Source, DestMax);
SourceLen = StrnLenS (Source, MIN (DestMax, Length));
if (Length >= DestMax) {
SAFE_STRING_CONSTRAINT_CHECK ((DestMax > SourceLen), RETURN_BUFFER_TOO_SMALL);
}
@ -361,7 +361,7 @@ StrnCpyS (
// pointed to by Destination. If no null character was copied from Source, then Destination[Length] is set to a null
// character.
//
while ((*Source != 0) && (SourceLen > 0)) {
while ((SourceLen > 0) && (*Source != 0)) {
*(Destination++) = *(Source++);
SourceLen--;
}
@ -551,7 +551,7 @@ StrnCatS (
//
// 5. If Length is not less than CopyLen, then CopyLen shall be greater than StrnLenS(Source, CopyLen).
//
SourceLen = StrnLenS (Source, CopyLen);
SourceLen = StrnLenS (Source, MIN (CopyLen, Length));
if (Length >= CopyLen) {
SAFE_STRING_CONSTRAINT_CHECK ((CopyLen > SourceLen), RETURN_BUFFER_TOO_SMALL);
}
@ -572,7 +572,7 @@ StrnCatS (
// a null character.
//
Destination = Destination + DestLen;
while ((*Source != 0) && (SourceLen > 0)) {
while ((SourceLen > 0) && (*Source != 0)) {
*(Destination++) = *(Source++);
SourceLen--;
}
@ -1916,7 +1916,7 @@ AsciiStrnCpyS (
//
// 4. If Length is not less than DestMax, then DestMax shall be greater than AsciiStrnLenS(Source, DestMax).
//
SourceLen = AsciiStrnLenS (Source, DestMax);
SourceLen = AsciiStrnLenS (Source, MIN (DestMax, Length));
if (Length >= DestMax) {
SAFE_STRING_CONSTRAINT_CHECK ((DestMax > SourceLen), RETURN_BUFFER_TOO_SMALL);
}
@ -1935,7 +1935,7 @@ AsciiStrnCpyS (
// pointed to by Destination. If no null character was copied from Source, then Destination[Length] is set to a null
// character.
//
while ((*Source != 0) && (SourceLen > 0)) {
while ((SourceLen > 0) && (*Source != 0)) {
*(Destination++) = *(Source++);
SourceLen--;
}
@ -2115,7 +2115,7 @@ AsciiStrnCatS (
//
// 5. If Length is not less than CopyLen, then CopyLen shall be greater than AsciiStrnLenS(Source, CopyLen).
//
SourceLen = AsciiStrnLenS (Source, CopyLen);
SourceLen = AsciiStrnLenS (Source, MIN (CopyLen, Length));
if (Length >= CopyLen) {
SAFE_STRING_CONSTRAINT_CHECK ((CopyLen > SourceLen), RETURN_BUFFER_TOO_SMALL);
}
@ -2136,7 +2136,7 @@ AsciiStrnCatS (
// a null character.
//
Destination = Destination + DestLen;
while ((*Source != 0) && (SourceLen > 0)) {
while ((SourceLen > 0) && (*Source != 0)) {
*(Destination++) = *(Source++);
SourceLen--;
}