[asan] Add test for deferencing zero-sized malloc/calloc#155933
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[asan] Add test for deferencing zero-sized malloc/calloc#155933
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ASan fails to catch this, because 0-byte allocations are converted into 1-byte allocations. Bug originally reported by dvyukov
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: Thurston Dang (thurstond) ChangesASan fails to catch this, because 0-byte allocations are converted into 1-byte allocations. Bug originally reported by dvyukov Full diff: https://github.com/llvm/llvm-project/pull/155933.diff 1 Files Affected:
diff --git a/compiler-rt/test/asan/TestCases/zero_alloc.cpp b/compiler-rt/test/asan/TestCases/zero_alloc.cpp
new file mode 100644
index 0000000000000..3decd5acb7bae
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/zero_alloc.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_asan -Wno-alloc-size -fsanitize-recover=address %s -o %t && %env_asan_opts=halt_on_error=0 %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: ERROR: AddressSanitizer: heap-buffer-overflow
+ // 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: ERROR: AddressSanitizer: heap-buffer-overflow
+ // 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: ERROR: AddressSanitizer: heap-buffer-overflow
+ // CHECK: {{#0 0x.* in main .*zero_alloc.cpp:}}[[@LINE-2]]
+ free(p3);
+ }
+
+ return 0;
+}
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fmayer
approved these changes
Aug 28, 2025
| @@ -0,0 +1,37 @@ | |||
| // RUN: %clang_asan -Wno-alloc-size -fsanitize-recover=address %s -o %t && %env_asan_opts=halt_on_error=0 %run %t 2>&1 | FileCheck %s | |||
|
|
|||
| // XFAIL: * | |||
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Added note on bad compiler is bad
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✅ With the latest revision this PR passed the C/C++ code formatter. |
thurstond
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Aug 28, 2025
When a zero-byte allocation is requested, ASan actually allocates 1-byte for compatibility. This change poisons that byte, to detect dereferences. Also updates the test from llvm#155933
thurstond
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that referenced
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Aug 29, 2025
When a zero-byte allocation is requested, ASan actually allocates 1-byte for compatibility. This change poisons that byte, to detect dereferences. Also updates the test from #155933
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ASan fails to catch this, because 0-byte allocations are converted into 1-byte allocations.
Bug originally reported by dvyukov