[llvm] r336011 - [HWASan] Do not retag allocas before return from the function.
Alex Shlyapnikov via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 29 13:20:18 PDT 2018
Author: alekseyshl
Date: Fri Jun 29 13:20:17 2018
New Revision: 336011
URL: http://llvm.org/viewvc/llvm-project?rev=336011&view=rev
Log:
[HWASan] Do not retag allocas before return from the function.
Summary:
Retagging allocas before returning from the function might help
detecting use after return bugs, but it does not work at all in real
life, when instrumented and non-instrumented code is intermixed.
Consider the following code:
F_non_instrumented() {
T x;
F1_instrumented(&x);
...
}
{
F_instrumented();
F_non_instrumented();
}
- F_instrumented call leaves the stack below the current sp tagged
randomly for UAR detection
- F_non_instrumented allocates its own vars on that tagged stack,
not generating any tags, that is the address of x has tag 0, but the
shadow memory still contains tags left behind by F_instrumented on the
previous step
- F1_instrumented verifies &x before using it and traps on tag mismatch,
0 vs whatever tag was set by F_instrumented
Reviewers: eugenis
Subscribers: srhines, llvm-commits
Differential Revision: https://reviews.llvm.org/D48664
Added:
llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll
Modified:
llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca.ll
Modified: llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp?rev=336011&r1=336010&r2=336011&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp Fri Jun 29 13:20:17 2018
@@ -95,6 +95,14 @@ static cl::opt<bool> ClInstrumentStack("
cl::desc("instrument stack (allocas)"),
cl::Hidden, cl::init(true));
+static cl::opt<bool> ClUARRetagToZero(
+ "hwasan-uar-retag-to-zero",
+ cl::desc("Clear alloca tags before returning from the function to allow "
+ "non-instrumented and instrumented function calls mix. When set "
+ "to false, allocas are retagged before returning from the "
+ "function to detect use after return."),
+ cl::Hidden, cl::init(true));
+
static cl::opt<bool> ClGenerateTagsWithCalls(
"hwasan-generate-tags-with-calls",
cl::desc("generate new tags with runtime library calls"), cl::Hidden,
@@ -577,6 +585,8 @@ Value *HWAddressSanitizer::getAllocaTag(
}
Value *HWAddressSanitizer::getUARTag(IRBuilder<> &IRB, Value *StackTag) {
+ if (ClUARRetagToZero)
+ return ConstantInt::get(IntptrTy, 0);
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
return IRB.CreateXor(StackTag, ConstantInt::get(IntptrTy, 0xFFU));
Added: llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll?rev=336011&view=auto
==============================================================================
--- llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll (added)
+++ llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll Fri Jun 29 13:20:17 2018
@@ -0,0 +1,22 @@
+; Test alloca instrumentation when tags are generated by HWASan function.
+;
+; RUN: opt < %s -hwasan -hwasan-generate-tags-with-calls -S | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-android"
+
+declare void @use32(i32*)
+
+define void @test_alloca() sanitize_hwaddress {
+; CHECK-LABEL: @test_alloca(
+; CHECK: %[[T1:[^ ]*]] = call i8 @__hwasan_generate_tag()
+; CHECK: %[[A:[^ ]*]] = zext i8 %[[T1]] to i64
+; CHECK: %[[B:[^ ]*]] = ptrtoint i32* %x to i64
+; CHECK: %[[C:[^ ]*]] = shl i64 %[[A]], 56
+; CHECK: or i64 %[[B]], %[[C]]
+
+entry:
+ %x = alloca i32, align 4
+ call void @use32(i32* nonnull %x)
+ ret void
+}
Modified: llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca.ll?rev=336011&r1=336010&r2=336011&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca.ll (original)
+++ llvm/trunk/test/Instrumentation/HWAddressSanitizer/alloca.ll Fri Jun 29 13:20:17 2018
@@ -1,8 +1,8 @@
-; Test basic address sanitizer instrumentation.
+; Test alloca instrumentation.
;
-; RUN: opt < %s -hwasan -S | FileCheck %s --check-prefixes=CHECK,DYNAMIC-SHADOW
-; RUN: opt < %s -hwasan -hwasan-mapping-offset=0 -S | FileCheck %s --check-prefixes=CHECK,ZERO-BASED-SHADOW
-; RUN: opt < %s -hwasan -hwasan-generate-tags-with-calls -S | FileCheck %s --check-prefix=WITH-CALLS
+; RUN: opt < %s -hwasan -S | FileCheck %s --check-prefixes=CHECK,DYNAMIC-SHADOW,NO-UAR-TAGS
+; RUN: opt < %s -hwasan -hwasan-mapping-offset=0 -S | FileCheck %s --check-prefixes=CHECK,ZERO-BASED-SHADOW,NO-UAR-TAGS
+; RUN: opt < %s -hwasan -hwasan-uar-retag-to-zero=0 -S | FileCheck %s --check-prefixes=CHECK,DYNAMIC-SHADOW,UAR-TAGS
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-android"
@@ -32,14 +32,15 @@ define void @test_alloca() sanitize_hwad
; CHECK: call void @llvm.memset.p0i8.i64(i8* align 1 %[[X_SHADOW]], i8 %[[X_TAG2]], i64 1, i1 false)
; CHECK: call void @use32(i32* nonnull %[[X_HWASAN]])
-; CHECK: %[[X_TAG_UAR:[^ ]*]] = xor i64 %[[BASE_TAG]], 255
-; CHECK: %[[X_TAG_UAR2:[^ ]*]] = trunc i64 %[[X_TAG_UAR]] to i8
+; UAR-TAGS: %[[BASE_TAG_COMPL:[^ ]*]] = xor i64 %[[BASE_TAG]], 255
+; UAR-TAGS: %[[X_TAG_UAR:[^ ]*]] = trunc i64 %[[BASE_TAG_COMPL]] to i8
; CHECK: %[[E2:[^ ]*]] = ptrtoint i32* %[[X]] to i64
; CHECK: %[[F2:[^ ]*]] = lshr i64 %[[E2]], 4
; DYNAMIC-SHADOW: %[[F2_DYN:[^ ]*]] = add i64 %[[F2]], %.hwasan.shadow
; DYNAMIC-SHADOW: %[[X_SHADOW2:[^ ]*]] = inttoptr i64 %[[F2_DYN]] to i8*
; ZERO-BASED-SHADOW: %[[X_SHADOW2:[^ ]*]] = inttoptr i64 %[[F2]] to i8*
-; CHECK: call void @llvm.memset.p0i8.i64(i8* align 1 %[[X_SHADOW2]], i8 %[[X_TAG_UAR2]], i64 1, i1 false)
+; NO-UAR-TAGS: call void @llvm.memset.p0i8.i64(i8* align 1 %[[X_SHADOW2]], i8 0, i64 1, i1 false)
+; UAR-TAGS: call void @llvm.memset.p0i8.i64(i8* align 1 %[[X_SHADOW2]], i8 %[[X_TAG_UAR]], i64 1, i1 false)
; CHECK: ret void
@@ -48,10 +49,3 @@ entry:
call void @use32(i32* nonnull %x)
ret void
}
-
-; WITH-CALLS-LABEL: @test_alloca(
-; WITH-CALLS: %[[T1:[^ ]*]] = call i8 @__hwasan_generate_tag()
-; WITH-CALLS: %[[A:[^ ]*]] = zext i8 %[[T1]] to i64
-; WITH-CALLS: %[[B:[^ ]*]] = ptrtoint i32* %x to i64
-; WITH-CALLS: %[[C:[^ ]*]] = shl i64 %[[A]], 56
-; WITH-CALLS: or i64 %[[B]], %[[C]]
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