[compiler-rt] [SanitizerCommon] add null check for fopen64 interceptor (PR #68760)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Wu Yingcong (yingcong-wu)

<details>
<summary>Changes</summary>

Currently, the interceptor for fopen64 will crash when path is null. Adding the same null check as `fopen()`.

---
Full diff: https://github.com/llvm/llvm-project/pull/68760.diff


2 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc (+1-1) 
- (added) compiler-rt/test/sanitizer_common/TestCases/fopen64_nullptr.c (+9) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
index 80efaf54a0607f6..4da29d928fcc236 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -6145,7 +6145,7 @@ INTERCEPTOR(int, flopenat, int dirfd, const char *path, int flags, ...) {
 INTERCEPTOR(__sanitizer_FILE *, fopen64, const char *path, const char *mode) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, fopen64, path, mode);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, path, internal_strlen(path) + 1);
+  if (path) COMMON_INTERCEPTOR_READ_RANGE(ctx, path, internal_strlen(path) + 1);
   COMMON_INTERCEPTOR_READ_RANGE(ctx, mode, internal_strlen(mode) + 1);
   __sanitizer_FILE *res = REAL(fopen64)(path, mode);
   COMMON_INTERCEPTOR_FILE_OPEN(ctx, res, path);
diff --git a/compiler-rt/test/sanitizer_common/TestCases/fopen64_nullptr.c b/compiler-rt/test/sanitizer_common/TestCases/fopen64_nullptr.c
new file mode 100644
index 000000000000000..2c260865c80a792
--- /dev/null
+++ b/compiler-rt/test/sanitizer_common/TestCases/fopen64_nullptr.c
@@ -0,0 +1,9 @@
+// Check that fopen64(NULL, "r") is ok.
+// `-m32` and `-D_FILE_OFFSET_BITS=64` will make fopen() call fopen64()
+
+// REQUIRES: asan
+// RUN: %clang -m32 -D_FILE_OFFSET_BITS=64 -O2 %s -o %t && %run %t
+#include <stdio.h>
+const char *fn = NULL;
+FILE *f;
+int main() { f = fopen(fn, "r"); }

``````````

</details>


https://github.com/llvm/llvm-project/pull/68760