[llvm] r197178 - Fix a use-after-free error in GlobalOpt CleanupConstantGlobalUsers

[Hal Finkel]

Author: hfinkel
Date: Thu Dec 12 14:45:24 2013
New Revision: 197178

URL: http://llvm.org/viewvc/llvm-project?rev=197178&view=rev
Log:
Fix a use-after-free error in GlobalOpt CleanupConstantGlobalUsers

GlobalOpt's CleanupConstantGlobalUsers function uses a worklist array to manage
constant users to be visited. The pointers in this array need to be weak
handles because when we delete a constant array, we may also be holding a
pointer to one of its elements (or an element of one of its elements if we're
dealing with an array of arrays) in the worklist.

Fixes PR17347.

Added:
    llvm/trunk/test/Transforms/GlobalOpt/array-elem-refs.ll
Modified:
    llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp

Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=197178&r1=197177&r2=197178&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Thu Dec 12 14:45:24 2013
@@ -37,6 +37,7 @@
 #include "llvm/Support/GetElementPtrTypeIterator.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ValueHandle.h"
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Transforms/Utils/GlobalStatus.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
@@ -267,9 +268,17 @@ static bool CleanupPointerRootUsers(Glob
 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
                                        DataLayout *TD, TargetLibraryInfo *TLI) {
   bool Changed = false;
-  SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
+  // Note that we need to use a weak value handle for the worklist items. When
+  // we delete a constant array, we may also be holding pointer to one of its
+  // elements (or an element of one of its elements if we're dealing with an
+  // array of arrays) in the worklist.
+  SmallVector<WeakVH, 8> WorkList(V->use_begin(), V->use_end());
   while (!WorkList.empty()) {
-    User *U = WorkList.pop_back_val();
+    Value *UV = WorkList.pop_back_val();
+    if (!UV)
+      continue;
+
+    User *U = cast<User>(UV);
 
     if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
       if (Init) {

Added: llvm/trunk/test/Transforms/GlobalOpt/array-elem-refs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalOpt/array-elem-refs.ll?rev=197178&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalOpt/array-elem-refs.ll (added)
+++ llvm/trunk/test/Transforms/GlobalOpt/array-elem-refs.ll Thu Dec 12 14:45:24 2013
@@ -0,0 +1,32 @@
+; RUN: opt < %s -S -globalopt | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.S = type { i8, i8 }
+
+ at c = internal global i8** bitcast (i8* getelementptr (i8* bitcast ([8 x i8*]* @b to i8*), i64 48) to i8**), align 8
+ at b = internal global [8 x i8*] [i8* null, i8* null, i8* null, i8* null, i8* null, i8* null, i8* getelementptr inbounds (%struct.S* @a, i32 0, i32 0), i8* getelementptr (i8* getelementptr inbounds (%struct.S* @a, i32 0, i32 0), i64 1)], align 16
+ at a = internal global %struct.S zeroinitializer, align 1
+
+; Function Attrs: nounwind uwtable
+define signext i8 @foo() #0 {
+entry:
+  %0 = load i8*** @c, align 8
+  %1 = load i8** %0, align 8
+  %2 = load i8* %1, align 1
+  ret i8 %2
+
+; CHECK-LABEL: @foo
+; CHECK: ret i8 0
+}
+
+; Function Attrs: nounwind uwtable
+define i32 @main() #0 {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval
+  ret i32 0
+}
+
+attributes #0 = { nounwind uwtable }
+