[PATCH] D48250: [sanitizer_common] Use O_TRUNC for WrOnly access mode.

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: glider, timurrrr.
Herald added subscribers: Sanitizers, llvm-commits, delcypher, kubamracek.

Otherwise if the file existed and was larger than the write size before the OpenFile call, the file will not be truncated and contain garbage in trailing bytes.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D48250

Files:
  lib/sanitizer_common/sanitizer_posix.cc


Index: lib/sanitizer_common/sanitizer_posix.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix.cc
+++ lib/sanitizer_common/sanitizer_posix.cc
@@ -160,7 +160,7 @@
   int flags;
   switch (mode) {
     case RdOnly: flags = O_RDONLY; break;
-    case WrOnly: flags = O_WRONLY | O_CREAT; break;
+    case WrOnly: flags = O_WRONLY | O_CREAT | O_TRUNC; break;
     case RdWr: flags = O_RDWR | O_CREAT; break;
   }
   fd_t res = internal_open(filename, flags, 0660);


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