From: Laszlo Ersek <lersek@redhat.com>
Date: Thu, 21 Jan 2016 18:40:09 +0000 (+0000)
Subject: ShellPkg: BcfgDisplayDump(): enforce minimum size for Boot#### and co.
X-Git-Tag: edk2-stable201903~7986
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=e5945ef78463a2a90631c91e9f8cff109fd20625

ShellPkg: BcfgDisplayDump(): enforce minimum size for Boot#### and co.

"3.1.1 Boot Manager Programming" in the UEFI 2.5 spec mandates that
Boot#### and similar options contain EFI_LOAD_OPTION structures. The
EFI_LOAD_OPTION structure encodes the fixed initial part of the payload,
and we can (and should) use it to enforce a minimum size for variable
contents.

This patch is meant as a safety improvement.

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ryan Harkin <ryan.harkin@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19710 6f19259b-4bc3-4df7-8a09-765794883524
---

diff --git a/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.c b/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.c
index 36d04d495c..9955c9e640 100644
--- a/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.c
+++ b/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.c
@@ -1052,6 +1052,7 @@ BcfgDisplayDump(
   CHAR16          *DevPathString;
   VOID            *DevPath;
   UINTN           Errors;
+  EFI_LOAD_OPTION *LoadOption;
 
   if (OrderCount == 0) {
     ShellPrintHiiEx(-1, -1, NULL, STRING_TOKEN(STR_BCFG_NONE), gShellBcfgHiiHandle, L"bcfg");  
@@ -1090,6 +1091,24 @@ BcfgDisplayDump(
       goto Cleanup;
     }
 
+    //
+    // We expect the Attributes, FilePathListLength, and L'\0'-terminated
+    // Description fields to be present.
+    //
+    if (BufferSize < sizeof *LoadOption + sizeof (CHAR16)) {
+      ShellPrintHiiEx (
+        -1,
+        -1,
+        NULL,
+        STRING_TOKEN (STR_BCFG_VAR_CORRUPT),
+        gShellBcfgHiiHandle,
+        L"bcfg",
+        VariableName
+        );
+      ++Errors;
+      goto Cleanup;
+    }
+
     if ((*(UINT16*)(Buffer+4)) != 0) {
       DevPath = AllocateZeroPool(*(UINT16*)(Buffer+4));
       if (DevPath != NULL) {
diff --git a/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.uni b/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.uni
index 25bd138b2b..282494b2f4 100644
--- a/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.uni
+++ b/ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.uni
@@ -37,6 +37,7 @@
 #string STR_GEN_OUT_MEM           #language en-US "%H%s%N: Memory allocation was not successful.\r\n"
 #string STR_BCFG_WRITE_FAIL       #language en-US "%H%s%N: Unable to write to '%H%s%N'\r\n"
 #string STR_BCFG_READ_FAIL        #language en-US "%H%s%N: Unable to read from '%H%s%N'\r\n"
+#string STR_BCFG_VAR_CORRUPT      #language en-US "%H%s%N: Variable '%H%s%N' corrupt.\r\n"
 #string STR_BCFG_HANDLE           #language en-US "%H%s%N: The handle [%H%02x%N] does not have DevicePath.\r\n"
 #string STR_BCFG_FILE             #language en-US "%H%s%N: The file '%H%s%N' matches multiple files.\r\n"
 #string STR_BCFG_FILE_OPEN        #language en-US "%H%s%N: The file '%H%s%N' did not open.\r\n"