(set_fd_flags): Handle file-creation flags on file

descriptors, rather than ignoring them.

1 files changed, 34 insertions, 2 deletions

diff --git a/src/dd.c b/src/dd.c
index b2bdf118c..b8512fbb5 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -1325,12 +1325,44 @@ copy_with_unblock (char const *buf, size_t nread)
 static void
 set_fd_flags (int fd, int add_flags, char const *name)
 {
+  /* Ignore file creation flags that are no-ops on file descriptors.  */
+  add_flags &= ~ (O_NOCTTY | O_NOFOLLOW);
+
   if (add_flags)
     {
       int old_flags = fcntl (fd, F_GETFL);
       int new_flags = old_flags | add_flags;
-      if (old_flags < 0
-	  || (new_flags != old_flags && fcntl (fd, F_SETFL, new_flags) == -1))
+      bool ok = true;
+      if (old_flags < 0)
+	ok = false;
+      else if (old_flags != new_flags)
+	{
+	  if (new_flags & (O_DIRECTORY | O_NOLINKS))
+	    {
+	      /* NEW_FLAGS contains at least one file creation flag that
+		 requires some checking of the open file descriptor.  */
+	      struct stat st;
+	      if (fstat (fd, &st) != 0)
+		ok = false;
+	      else if ((new_flags & O_DIRECTORY) && ! S_ISDIR (st.st_mode))
+		{
+		  errno = ENOTDIR;
+		  ok = false;
+		}
+	      else if ((new_flags & O_NOLINKS) && 1 < st.st_nlink)
+		{
+		  errno = EMLINK;
+		  ok = false;
+		}
+	      new_flags &= ~ (O_DIRECTORY | O_NOLINKS);
+	    }
+
+	  if (ok && old_flags != new_flags
+	      && fcntl (fd, F_SETFL, new_flags) == -1)
+	    ok = false;
+	}
+
+      if (!ok)
 	error (EXIT_FAILURE, errno, _("setting flags for %s"), quote (name));
     }
 }