libfuzzer: Fix file listing on some filesystems

[chouquette]

Summary

For some filesystems, readdir will not populate dirent::d_type with valuable information. This causes libfuzzer to proceed with an empty corpus, instead of the file it contains.

This has been tested on a server using XFS.

It should fix https://bugs.llvm.org//show_bug.cgi?id=25991

[kcc]

My usual question: is a test possible?

lib/fuzzer/FuzzerIOPosix.cpp

35

Please make this static, since it's not used outside of this file.

[chouquette]

• Making IsDirectory static

[chouquette]

I'm not sure a test is possible without abstracting all calls to opendir/readdir/stat, allowing them to be mocked. Unless you had something more specific in mind?

[kcc]

LGTM

[chouquette]

Thanks for the review!

I suppose I'll need someone to push this for me as I don't have access.

lib/fuzzer/FuzzerIOPosix.cpp

 
 bool IsFile(const std::string &Path) {
   struct stat St;
   if (stat(Path.c_str(), &St))
     return false;
   return S_ISREG(St.st_mode);
 }
 
+static bool IsDirectory(const std::string &Path) {
+  struct stat St;
+  if (stat(Path.c_str(), &St))
+    return false;
+  return S_ISDIR(St.st_mode);
+}
+
 size_t FileSize(const std::string &Path) {
   struct stat St;
   if (stat(Path.c_str(), &St))
     return 0;
   return St.st_size;
 }
 
 void ListFilesInDirRecursive(const std::string &Dir, long *Epoch,
                              Vector<std::string> *V, bool TopDir) {
   auto E = GetEpoch(Dir);
   if (Epoch)
     if (E && *Epoch >= E) return;
 
   DIR *D = opendir(Dir.c_str());
   if (!D) {
     Printf("No such directory: %s; exiting\n", Dir.c_str());
     exit(1);
   }
   while (auto E = readdir(D)) {
     std::string Path = DirPlusFile(Dir, E->d_name);
-    if (E->d_type == DT_REG || E->d_type == DT_LNK)
+    if (E->d_type == DT_REG || E->d_type == DT_LNK ||
+        (E->d_type == DT_UNKNOWN && IsFile(Path)))
       V->push_back(Path);
-    else if (E->d_type == DT_DIR && *E->d_name != '.')
+    else if ((E->d_type == DT_DIR ||
+             (E->d_type == DT_UNKNOWN && IsDirectory(Path))) &&
+             *E->d_name != '.')
       ListFilesInDirRecursive(Path, Epoch, V, false);
   }
   closedir(D);
   if (Epoch && TopDir)
     *Epoch = E;
 }
 
 char GetSeparator() {