https://github.com/gbMattN updated
https://github.com/llvm/llvm-project/pull/95387
>From 8099113d68bd7c47c29f635bb10a048ddb99833b Mon Sep 17 00:00:00 2001
From: Matthew Nagy <gbm...@tiger-linux2.domain.snsys.com>
Date: Fri, 28 Jun 2024 16:12:31 +0000
Subject: [PATCH] [TySan] Fixed false positive when accessing global object's
member variables
---
compiler-rt/lib/tysan/tysan.cpp | 19 +++++++++++-
.../test/tysan/global-struct-members.c | 31 +++++++++++++++++++
2 files changed, 49 insertions(+), 1 deletion(-)
create mode 100644 compiler-rt/test/tysan/global-struct-members.c
diff --git a/compiler-rt/lib/tysan/tysan.cpp b/compiler-rt/lib/tysan/tysan.cpp
index f627851d049e6..8235b0ec2b55e 100644
--- a/compiler-rt/lib/tysan/tysan.cpp
+++ b/compiler-rt/lib/tysan/tysan.cpp
@@ -221,7 +221,24 @@ __tysan_check(void *addr, int size, tysan_type_descriptor
*td, int flags) {
OldTDPtr -= i;
OldTD = *OldTDPtr;
- if (!isAliasingLegal(td, OldTD))
+ // When shadow memory is set for global objects, the entire object is
tagged with the struct type
+ // This means that when you access a member variable, tysan reads that as
you accessing a struct midway
+ // through, with 'i' being the offset
+ // Therefore, if you are accessing a struct, we need to find the member
type. We can go through the
+ // members of the struct type and see if there is a member at the offset
you are accessing the struct by.
+ // If there is indeed a member starting at offset 'i' in the struct, we
should check aliasing legality
+ // with that type. If there isn't, we run alias checking on the struct
with will give us the correct error.
+ tysan_type_descriptor *InternalMember = OldTD;
+ if (OldTD->Tag == TYSAN_STRUCT_TD) {
+ for (int j = 0; j < OldTD->Struct.MemberCount; j++) {
+ if (OldTD->Struct.Members[j].Offset == i) {
+ InternalMember = OldTD->Struct.Members[j].Type;
+ break;
+ }
+ }
+ }
+
+ if (!isAliasingLegal(td, InternalMember))
reportError(addr, size, td, OldTD, AccessStr,
"accesses part of an existing object", -i, pc, bp, sp);
diff --git a/compiler-rt/test/tysan/global-struct-members.c
b/compiler-rt/test/tysan/global-struct-members.c
new file mode 100644
index 0000000000000..76ea3c431dd7b
--- /dev/null
+++ b/compiler-rt/test/tysan/global-struct-members.c
@@ -0,0 +1,31 @@
+// RUN: %clang_tysan -O0 %s -o %t && %run %t >%t.out 2>&1
+// RUN: FileCheck %s < %t.out
+
+#include <stdio.h>
+
+struct X {
+ int a, b, c;
+} x;
+
+static struct X xArray[2];
+
+int main() {
+ x.a = 1;
+ x.b = 2;
+ x.c = 3;
+
+ printf("%d %d %d\n", x.a, x.b, x.c);
+ // CHECK-NOT: ERROR: TypeSanitizer: type-aliasing-violation
+
+ for (size_t i = 0; i < 2; i++) {
+ xArray[i].a = 1;
+ xArray[i].b = 1;
+ xArray[i].c = 1;
+ }
+
+ struct X *xPtr = (struct X *)&(xArray[0].c);
+ xPtr->a = 1;
+ // CHECK: ERROR: TypeSanitizer: type-aliasing-violation
+ // CHECK: WRITE of size 4 at {{.*}} with type int (in X at offset 0)
accesses an existing object of type int (in X at offset 8)
+ // CHECK: {{#0 0x.* in main .*struct-members.c:}}[[@LINE-3]]
+}
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