[compiler-rt] [compiler-rt] [libtsan] fix fstat{, 64} interceptors on glibc (PR #75578)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Miod Vallat (dustanddreams)

<details>
<summary>Changes</summary>

When targeting a glibc environment, the `fstat` and `fstat64` interceptors directly invoke `__fxstat64` rather than `fstat` and `fstat64`.

Unfortunately, the `__fxstat64` Linux interface is not machine-independent, as it takes a "`struct stat` version number" argument, which values vary across architectures and do not seem to be exposed in userland headers, as reported and analyzed in issue #<!-- -->75346.

This PR implements the suggested fix in the issue by invoking `fstat` and `fstat64` as expected, and letting them invoke `__fxstat64` with the proper, machine-specific, arguments.

---
Full diff: https://github.com/llvm/llvm-project/pull/75578.diff


1 Files Affected:

- (modified) compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp (+2-9) 


``````````diff
diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
index 80f86ca98ed9cd..28f6ccffcc4420 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -1603,17 +1603,10 @@ TSAN_INTERCEPTOR(int, __fxstat, int version, int fd, void *buf) {
 #endif
 
 TSAN_INTERCEPTOR(int, fstat, int fd, void *buf) {
-#if SANITIZER_GLIBC
-  SCOPED_TSAN_INTERCEPTOR(__fxstat, 0, fd, buf);
-  if (fd > 0)
-    FdAccess(thr, pc, fd);
-  return REAL(__fxstat)(0, fd, buf);
-#else
   SCOPED_TSAN_INTERCEPTOR(fstat, fd, buf);
   if (fd > 0)
     FdAccess(thr, pc, fd);
   return REAL(fstat)(fd, buf);
-#endif
 }
 
 #if SANITIZER_GLIBC
@@ -1630,10 +1623,10 @@ TSAN_INTERCEPTOR(int, __fxstat64, int version, int fd, void *buf) {
 
 #if SANITIZER_GLIBC
 TSAN_INTERCEPTOR(int, fstat64, int fd, void *buf) {
-  SCOPED_TSAN_INTERCEPTOR(__fxstat64, 0, fd, buf);
+  SCOPED_TSAN_INTERCEPTOR(fstat64, fd, buf);
   if (fd > 0)
     FdAccess(thr, pc, fd);
-  return REAL(__fxstat64)(0, fd, buf);
+  return REAL(fstat64)(fd, buf);
 }
 #define TSAN_MAYBE_INTERCEPT_FSTAT64 TSAN_INTERCEPT(fstat64)
 #else

``````````

</details>


https://github.com/llvm/llvm-project/pull/75578