Add MSan interceptor for fstat(2)

[krytarowski]

Summary

Add new MSan interceptor that corrects NetBSD's
specific handling of fstat(2).

NetBSD renames the call to __fstat50.

Add new test: test/msan/fstat.cc

Sponsored by <The NetBSD Foundation>

[vitalybuka]

Could you please add a test?

[krytarowski]

In D41637#965294, @vitalybuka wrote:

Could you please add a test?

I will do it.

[krytarowski]

Add test.

lib/msan/msan_interceptors.cc

 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_errno.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_tls_get_addr.h"
 
 #if SANITIZER_NETBSD
+#define fstat __fstat50
 #define gettimeofday __gettimeofday50
 #define getrusage __getrusage50
 #endif
 
 #include <stdarg.h>
 // ACHTUNG! No other system header includes in this file.
 // Ideally, we should get rid of stdarg.h as well.
 

 
 INTERCEPTOR(int, putenv, char *string) {
   ENSURE_MSAN_INITED();
   int res = REAL(putenv)(string);
   if (!res) UnpoisonEnviron();
   return res;
 }
 
+#if SANITIZER_NETBSD
+INTERCEPTOR(int, fstat, int fd, void *buf) {
+  ENSURE_MSAN_INITED();
+  int res = REAL(fstat)(fd, buf);
+  if (!res)
+    __msan_unpoison(buf, __sanitizer::struct_stat_sz);
+  return res;
+}
+#define MSAN_MAYBE_INTERCEPT_FSTAT INTERCEPT_FUNCTION(fstat)
+#else
+#define MSAN_MAYBE_INTERCEPT_FSTAT
+#endif
+
 #if !SANITIZER_FREEBSD && !SANITIZER_NETBSD
 INTERCEPTOR(int, __fxstat, int magic, int fd, void *buf) {
   ENSURE_MSAN_INITED();
   int res = REAL(__fxstat)(magic, fd, buf);
   if (!res)
     __msan_unpoison(buf, __sanitizer::struct_stat_sz);
   return res;
 }
#endif
   INTERCEPT_FUNCTION(wcscpy);
   INTERCEPT_FUNCTION(wcsncpy);
   INTERCEPT_FUNCTION(wcscmp);
   INTERCEPT_FUNCTION(getenv);
   INTERCEPT_FUNCTION(setenv);
   INTERCEPT_FUNCTION(putenv);
   INTERCEPT_FUNCTION(gettimeofday);
   MSAN_MAYBE_INTERCEPT_FCVT;
+  MSAN_MAYBE_INTERCEPT_FSTAT;
   MSAN_MAYBE_INTERCEPT___FXSTAT;
   MSAN_INTERCEPT_FSTATAT;
   MSAN_MAYBE_INTERCEPT___FXSTAT64;
   MSAN_MAYBE_INTERCEPT___FXSTATAT64;
   INTERCEPT_FUNCTION(pipe);
   INTERCEPT_FUNCTION(pipe2);
   INTERCEPT_FUNCTION(socketpair);
   INTERCEPT_FUNCTION(fgets);

test/msan/fstat.cc

+// RUN: %clangxx_msan -O0 %s -o %t && %run %t
+
+#include <sys/stat.h>
+#include <stdlib.h>
+
+int main(void) {
+  struct stat st;
+  if (fstat(0, &st))
+    exit(1);
+
+  if (S_ISBLK(st.st_mode))
+    exit(0);
+
+  return 0;
+}