edk2/edk2-OvmfPkg-VirtNorFlashDxe-sanity-check-variables.patch

From c4eef747624d41aaa09dc64ccafdb84bf1fe656e Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 9 Jan 2024 12:29:02 +0100
Subject: [PATCH 2/2] OvmfPkg/VirtNorFlashDxe: sanity-check variables

RH-Author: Gerd Hoffmann <None>
RH-MergeRequest: 42: OvmfPkg/VirtNorFlashDxe: sanity-check variables
RH-Jira: RHEL-17587
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [2/2] 56ff961f754d517c0e27ccf46a95b228efe7ab4b

Extend the ValidateFvHeader function, additionally to the header checks
walk over the list of variables and sanity check them.

In case we find inconsistencies indicating variable store corruption
return EFI_NOT_FOUND so the variable store will be re-initialized.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20240109112902.30002-4-kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
[lersek@redhat.com: fix StartId initialization/assignment coding style]
(cherry picked from commit 4a443f73fd67ca8caaf0a3e1a01f8231b330d2e0)
---
 .../Drivers/NorFlashDxe/NorFlashDxe.inf       |   1 +
 .../Drivers/NorFlashDxe/NorFlashFvb.c         | 149 +++++++++++++++++-
 2 files changed, 145 insertions(+), 5 deletions(-)

diff --git a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf
index f8d4c27031..10388880a1 100644
--- a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf
+++ b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.inf
@@ -35,6 +35,7 @@
   DebugLib
   HobLib
   NorFlashPlatformLib
+  SafeIntLib
   UefiLib
   UefiDriverEntryPoint
   UefiBootServicesTableLib
diff --git a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashFvb.c b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashFvb.c
index 904605cbbc..2a166c94a6 100644
--- a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashFvb.c
+++ b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashFvb.c
@@ -13,6 +13,7 @@
 #include <Library/UefiLib.h>
 #include <Library/BaseMemoryLib.h>
 #include <Library/MemoryAllocationLib.h>
+#include <Library/SafeIntLib.h>
 
 #include <Guid/VariableFormat.h>
 #include <Guid/SystemNvDataGuid.h>
@@ -166,11 +167,12 @@ ValidateFvHeader (
   IN  NOR_FLASH_INSTANCE *Instance
   )
 {
-  UINT16                      Checksum;
-  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader;
-  VARIABLE_STORE_HEADER       *VariableStoreHeader;
-  UINTN                       VariableStoreLength;
-  UINTN                       FvLength;
+  UINT16                            Checksum;
+  CONST EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader;
+  CONST VARIABLE_STORE_HEADER       *VariableStoreHeader;
+  UINTN                             VarOffset;
+  UINTN                             VariableStoreLength;
+  UINTN                             FvLength;
 
   FwVolHeader = (EFI_FIRMWARE_VOLUME_HEADER*)Instance->RegionBaseAddress;
 
@@ -223,6 +225,143 @@ ValidateFvHeader (
     return EFI_NOT_FOUND;
   }
 
+  //
+  // check variables
+  //
+  DEBUG ((DEBUG_INFO, "%a: checking variables\n", __func__));
+  VarOffset = sizeof (*VariableStoreHeader);
+  for ( ; ;) {
+    UINTN                                VarHeaderEnd;
+    UINTN                                VarNameEnd;
+    UINTN                                VarEnd;
+    UINTN                                VarPadding;
+    CONST AUTHENTICATED_VARIABLE_HEADER  *VarHeader;
+    CONST CHAR16                         *VarName;
+    CONST CHAR8                          *VarState;
+    RETURN_STATUS                        Status;
+
+    Status = SafeUintnAdd (VarOffset, sizeof (*VarHeader), &VarHeaderEnd);
+    if (RETURN_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: integer overflow\n", __func__));
+      return EFI_NOT_FOUND;
+    }
+
+    if (VarHeaderEnd >= VariableStoreHeader->Size) {
+      if (VarOffset <= VariableStoreHeader->Size - sizeof (UINT16)) {
+        CONST UINT16  *StartId;
+
+        StartId = (VOID *)((UINTN)VariableStoreHeader + VarOffset);
+        if (*StartId == 0x55aa) {
+          DEBUG ((DEBUG_ERROR, "%a: startid at invalid location\n", __func__));
+          return EFI_NOT_FOUND;
+        }
+      }
+
+      DEBUG ((DEBUG_INFO, "%a: end of var list (no space left)\n", __func__));
+      break;
+    }
+
+    VarHeader = (VOID *)((UINTN)VariableStoreHeader + VarOffset);
+    if (VarHeader->StartId != 0x55aa) {
+      DEBUG ((DEBUG_INFO, "%a: end of var list (no startid)\n", __func__));
+      break;
+    }
+
+    VarName = NULL;
+    switch (VarHeader->State) {
+      // usage: State = VAR_HEADER_VALID_ONLY
+      case VAR_HEADER_VALID_ONLY:
+        VarState = "header-ok";
+        VarName  = L"<unknown>";
+        break;
+
+      // usage: State = VAR_ADDED
+      case VAR_ADDED:
+        VarState = "ok";
+        break;
+
+      // usage: State &= VAR_IN_DELETED_TRANSITION
+      case VAR_ADDED &VAR_IN_DELETED_TRANSITION:
+        VarState = "del-in-transition";
+        break;
+
+      // usage: State &= VAR_DELETED
+      case VAR_ADDED &VAR_DELETED:
+      case VAR_ADDED &VAR_DELETED &VAR_IN_DELETED_TRANSITION:
+        VarState = "deleted";
+        break;
+
+      default:
+        DEBUG ((
+          DEBUG_ERROR,
+          "%a: invalid variable state: 0x%x\n",
+          __func__,
+          VarHeader->State
+          ));
+        return EFI_NOT_FOUND;
+    }
+
+    Status = SafeUintnAdd (VarHeaderEnd, VarHeader->NameSize, &VarNameEnd);
+    if (RETURN_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: integer overflow\n", __func__));
+      return EFI_NOT_FOUND;
+    }
+
+    Status = SafeUintnAdd (VarNameEnd, VarHeader->DataSize, &VarEnd);
+    if (RETURN_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: integer overflow\n", __func__));
+      return EFI_NOT_FOUND;
+    }
+
+    if (VarEnd > VariableStoreHeader->Size) {
+      DEBUG ((
+        DEBUG_ERROR,
+        "%a: invalid variable size: 0x%Lx + 0x%Lx + 0x%x + 0x%x > 0x%x\n",
+        __func__,
+        (UINT64)VarOffset,
+        (UINT64)(sizeof (*VarHeader)),
+        VarHeader->NameSize,
+        VarHeader->DataSize,
+        VariableStoreHeader->Size
+        ));
+      return EFI_NOT_FOUND;
+    }
+
+    if (((VarHeader->NameSize & 1) != 0) ||
+        (VarHeader->NameSize < 4))
+    {
+      DEBUG ((DEBUG_ERROR, "%a: invalid name size\n", __func__));
+      return EFI_NOT_FOUND;
+    }
+
+    if (VarName == NULL) {
+      VarName = (VOID *)((UINTN)VariableStoreHeader + VarHeaderEnd);
+      if (VarName[VarHeader->NameSize / 2 - 1] != L'\0') {
+        DEBUG ((DEBUG_ERROR, "%a: name is not null terminated\n", __func__));
+        return EFI_NOT_FOUND;
+      }
+    }
+
+    DEBUG ((
+      DEBUG_VERBOSE,
+      "%a: +0x%04Lx: name=0x%x data=0x%x guid=%g '%s' (%a)\n",
+      __func__,
+      (UINT64)VarOffset,
+      VarHeader->NameSize,
+      VarHeader->DataSize,
+      &VarHeader->VendorGuid,
+      VarName,
+      VarState
+      ));
+
+    VarPadding = (4 - (VarEnd & 3)) & 3;
+    Status     = SafeUintnAdd (VarEnd, VarPadding, &VarOffset);
+    if (RETURN_ERROR (Status)) {
+      DEBUG ((DEBUG_ERROR, "%a: integer overflow\n", __func__));
+      return EFI_NOT_FOUND;
+    }
+  }
+
   return EFI_SUCCESS;
 }
 
-- 
2.41.0