[PATCH] D156798: Check if directory before opening file

[Aaron Ballman via Phabricator via llvm-commits]

aaron.ballman requested changes to this revision.
aaron.ballman added a comment.
This revision now requires changes to proceed.

Please add comments to the patch description explaining what's changing and why (this helps reviewers as well as during code archeology after the changes land).



================
Comment at: llvm/lib/Support/Unix/Path.inc:17
 //===----------------------------------------------------------------------===//
-
+#include <iostream> 
 #include "Unix.h"
----------------
Please do not include `iostream`: https://llvm.org/docs/CodingStandards.html#include-iostream-is-forbidden


================
Comment at: llvm/lib/Support/Unix/Path.inc:1017-1024
+  
+  if (Access == FA_Read) {
+    struct stat Status;
+    if (stat(P.begin(), &Status) == -1) 
+      return std::error_code(errno, std::generic_category());
+    if (S_ISDIR(Status.st_mode))
+      return make_error_code(errc::is_a_directory);
----------------
This introduces a TOCTOU issue with the code -- there's now a window where `stat` will return the status of the file but that status can change before the call to `open`.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156798/new/

https://reviews.llvm.org/D156798