[msan] Add test for deferencing zero-sized malloc/calloc #155934
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@llvm/pr-subscribers-llvm-transforms Author: Thurston Dang (thurstond) ChangesFull diff: https://github.com/llvm/llvm-project/pull/155934.diff 2 Files Affected:
diff --git a/compiler-rt/test/msan/zero_alloc.cpp b/compiler-rt/test/msan/zero_alloc.cpp
new file mode 100644
index 0000000000000..4b60c161efb36
--- /dev/null
+++ b/compiler-rt/test/msan/zero_alloc.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_msan -Wno-alloc-size -fsanitize-recover=memory %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// XFAIL: *
+
+#include <malloc.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+ {
+ char* p1 = (char*)calloc(1, 0);
+ printf ("p1 is %p\n", p1);
+ printf ("Content of p1 is: %d\n", *p1);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p1);
+ }
+
+ {
+ char* p2 = (char*)calloc(0, 1);
+ printf ("p2 is %p\n", p2);
+ printf ("Content of p2 is: %d\n", *p2);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p2);
+ }
+
+ {
+ char* p3 = (char*)malloc(0);
+ printf ("p3 is %p\n", p3);
+ printf ("Content of p2 is: %d\n", *p3);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p3);
+ }
+
+ return 0;
+}
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index fc34d14259d1f..66cdbfcf998c6 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -1574,6 +1574,9 @@ void HWAddressSanitizer::sanitizeFunction(Function &F,
if (F.empty())
return;
+ if (F.isPresplitCoroutine())
+ return;
+
NumTotalFuncs++;
OptimizationRemarkEmitter &ORE =
|
|
@llvm/pr-subscribers-compiler-rt-sanitizer Author: Thurston Dang (thurstond) ChangesFull diff: https://github.com/llvm/llvm-project/pull/155934.diff 2 Files Affected:
diff --git a/compiler-rt/test/msan/zero_alloc.cpp b/compiler-rt/test/msan/zero_alloc.cpp
new file mode 100644
index 0000000000000..4b60c161efb36
--- /dev/null
+++ b/compiler-rt/test/msan/zero_alloc.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_msan -Wno-alloc-size -fsanitize-recover=memory %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// XFAIL: *
+
+#include <malloc.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+ {
+ char* p1 = (char*)calloc(1, 0);
+ printf ("p1 is %p\n", p1);
+ printf ("Content of p1 is: %d\n", *p1);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p1);
+ }
+
+ {
+ char* p2 = (char*)calloc(0, 1);
+ printf ("p2 is %p\n", p2);
+ printf ("Content of p2 is: %d\n", *p2);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p2);
+ }
+
+ {
+ char* p3 = (char*)malloc(0);
+ printf ("p3 is %p\n", p3);
+ printf ("Content of p2 is: %d\n", *p3);
+ // CHECK: WARNING: MemorySanitizer: use-of-uninitialized-value
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p3);
+ }
+
+ return 0;
+}
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index fc34d14259d1f..66cdbfcf998c6 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -1574,6 +1574,9 @@ void HWAddressSanitizer::sanitizeFunction(Function &F,
if (F.empty())
return;
+ if (F.isPresplitCoroutine())
+ return;
+
NumTotalFuncs++;
OptimizationRemarkEmitter &ORE =
|
MSan fails to catch this, because 0-byte allocations are converted into 1-byte allocations. Bug originally reported by dvyukov
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fmayer
approved these changes
Aug 28, 2025
thurstond
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Aug 28, 2025
When a zero-byte allocation is requested, MSan actually allocates 1-byte for compatibility. This change poisons that byte, to detect dereferences. Also updates the test from llvm#155934
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MSan fails to catch this, because 0-byte allocations are converted into 1-byte allocations.
Bug originally reported by dvyukov