Re: [PATCH v1 05/11] ShellPkg: acpiview: SLIT: Validate System Locality count

["Sami Mujawar" <sami.mujawar@arm.com>]

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Regards,

Sami Mujawar

-----Original Message-----
From: Krzysztof Koch <krzysztof.koch@arm.com> 
Sent: 15 August 2019 02:11 PM
To: devel@edk2.groups.io
Cc: jaben.carsey@intel.com; ray.ni@intel.com; zhichao.gao@intel.com; Sami Mujawar <Sami.Mujawar@arm.com>; Matteo Carlini <Matteo.Carlini@arm.com>; nd <nd@arm.com>
Subject: [PATCH v1 05/11] ShellPkg: acpiview: SLIT: Validate System Locality count

1. Check if the 'Number of System Localities' provided can be represented in the SLIT table. The table 'Length' field is a 32-bit value while the 'Number of System Localities' field is 64-bit long.

2. Check if the SLIT matrix fits in the table buffer. If N is the SLIT locality count, then the matrix used to represent the localities is N*N bytes long. The ACPI table length must be big enough to fit the matrix.

3. Remove (now) redundant 64x64 bit multiplication.

Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>
---

Notes:
    v1:
    - Validate the 'Number of System Localities' Field [Krzysztof]
    - Remove redundant 64x64 bit multiplication [Krzysztof]

 ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c | 47 +++++++++++++++++---
 1 file changed, 42 insertions(+), 5 deletions(-)

diff --git a/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c b/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c
index 17e2166a09d8615b714e0c51d4d93d293fcdf601..e4625ee8b13907893a9b6990ecb956baf91cc3b9 100644
--- a/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c
+++ b/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitPars
+++ er.c
@@ -30,7 +30,7 @@ STATIC CONST ACPI_PARSER SlitParser[] = {
 /**
   Macro to get the value of a System Locality  **/ -#define SLIT_ELEMENT(Ptr, i, j) *(Ptr + (MultU64x64 (i, LocalityCount)) + j)
+#define SLIT_ELEMENT(Ptr, i, j) *(Ptr + (i * LocalityCount) + j)
 
 /**
   This function parses the ACPI SLIT table.
@@ -57,9 +57,9 @@ ParseAcpiSlit (
   )
 {
   UINT32 Offset;
-  UINT64 Count;
-  UINT64 Index;
-  UINT64 LocalityCount;
+  UINT32 Count;
+  UINT32 Index;
+  UINT32 LocalityCount;
   UINT8* LocalityPtr;
   CHAR16 Buffer[80];  // Used for AsciiName param of ParseAcpi
 
@@ -87,8 +87,45 @@ ParseAcpiSlit (
     return;
   }
 
+  /*
+    Despite the 'Number of System Localities' being a 64-bit field in SLIT,
+    the maximum number of localities that can be represented in SLIT is limited
+    by the 'Length' field of the ACPI table.
+
+    Since the ACPI table length field is 32-bit wide. The maximum number of
+    localities that can be represented in SLIT can be calculated as:
+
+    MaxLocality = sqrt (MAX_UINT32 - sizeof (EFI_ACPI_6_3_SYSTEM_LOCALITY_DISTANCE_INFORMATION_TABLE_HEADER))
+                = 65535
+                = MAX_UINT16
+  */
+  if (*SlitSystemLocalityCount > MAX_UINT16) {
+    IncrementErrorCount ();
+    Print (
+      L"ERROR: The Number of System Localities provided can't be represented " \
+        L"in the SLIT table. SlitSystemLocalityCount = %ld. " \
+        L"MaxLocalityCountAllowed = %d.\n",
+      *SlitSystemLocalityCount,
+      MAX_UINT16
+      );
+    return;
+  }
+
+  LocalityCount = (UINT32)*SlitSystemLocalityCount;
+
+  // Make sure system localities fit in the table buffer provided  if 
+ (Offset + (LocalityCount * LocalityCount) > AcpiTableLength) {
+    IncrementErrorCount ();
+    Print (
+      L"ERROR: Invalid Number of System Localities. " \
+        L"SlitSystemLocalityCount = %ld. AcpiTableLength = %d.\n",
+      *SlitSystemLocalityCount,
+      AcpiTableLength
+      );
+    return;
+  }
+
   LocalityPtr = Ptr + Offset;
-  LocalityCount = *SlitSystemLocalityCount;
 
   // We only print the Localities if the count is less than 16
   // If the locality count is more than 16 then refer to the
--
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'