[edk2-devel] [PATCH] ShellPkg/Type.c: Add value check before (LoopVar - 1)

[Jim Dailey]

Zhichao,

I believe the same problem exists further into the function in the 'else'
clause handling UCS2 characters.

Regards,
Jim

-----Original Message-----
From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Gao, Zhichao
Sent: Monday, July 15, 2019 2:30 AM
To: devel at edk2.groups.io
Cc: Jaben Carsey; Ray Ni; Andrew Fish
Subject: [edk2-devel] [PATCH] ShellPkg/Type.c: Add value check before (LoopVar - 1)


[EXTERNAL EMAIL] 

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1964

If the file begin with single line Feed ('\n'), then
"AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r'"
would cause a underflow. Add this condition
"(AsciiChar == '\n' && LoopVar == 0)" before it to make sure
(LoopVar - 1) would never encounter a underflow.

Cc: Jaben Carsey <jaben.carsey at intel.com>
Cc: Ray Ni <ray.ni at intel.com>
Cc: Andrew Fish <afish at apple.com>
Signed-off-by: Zhichao Gao <zhichao.gao at intel.com>
---
 ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c b/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
index 4efc0a8e24..c1f670c713 100644
--- a/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
+++ b/ShellPkg/Library/UefiShellLevel3CommandsLib/Type.c
@@ -78,12 +78,13 @@ TypeFileByHandle (
           // Allow Line Feed (LF) (0xA) & Carriage Return (CR) (0xD)
           // characters to be displayed as is.
           //
-          if (AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r') {
+          if ((AsciiChar == '\n' && LoopVar == 0) ||
+              (AsciiChar == '\n' && ((CHAR8*)Buffer)[LoopVar-1] != '\r')) {
             //
-            // In case Line Feed (0xA) is encountered & Carriage Return (0xD)
-            // was not the previous character, print CR and LF. This is because
-            // Shell 2.0 requires carriage return with line feed for displaying
-            // each new line from left.
+            // In case file begin with single line Feed or Line Feed (0xA) is
+            // encountered & Carriage Return (0xD) was not previous character,
+            // print CR and LF. This is because Shell 2.0 requires carriage
+            // return Swith line feed for displaying each new line from left.
             //
             ShellPrintEx (-1, -1, L"\r\n");
             continue;
-- 
2.21.0.windows.1




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