Don't unpatch an unloaded module. We verify if the original function address is still valid

with a VirtualQuery call.

This fixes http://code.google.com/p/chromium/issues/detail?id=7701

Bug=7701


Review URL: http://codereview.chromium.org/21434

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@9929 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 19 insertions, 3 deletions

diff --git a/base/iat_patch.cc b/base/iat_patch.cc
index 713aa92..2417608 100644
--- a/base/iat_patch.cc
+++ b/base/iat_patch.cc
@@ -205,9 +205,25 @@ DWORD IATPatchFunction::Patch(HMODULE module_handle,
 }
 
 DWORD IATPatchFunction::Unpatch() {
-  DWORD error = RestoreImportedFunction(intercept_function_,
-                                        original_function_,
-                                        iat_thunk_);
+  DWORD error = 0;  
+  MEMORY_BASIC_INFORMATION memory_info = {0};
+
+  // If the module has already unloaded, no point trying to unpatch.
+  if (!VirtualQuery(original_function_, &memory_info,
+                    sizeof(memory_info))) {
+    error = GetLastError();
+    NOTREACHED();
+    return error;
+  }
+
+  if ((memory_info.State  & MEM_COMMIT) != MEM_COMMIT) {
+    NOTREACHED();
+    return ERROR_ACCESS_DENIED;
+  }
+
+  error = RestoreImportedFunction(intercept_function_,
+                                  original_function_,
+                                  iat_thunk_);
   DCHECK(NO_ERROR == error);
 
   // Hands off the intercept if we fail to unpatch.