From: Sergey Poznyakoff <gray@gnu.org>
Date: Fri, 8 Jan 2021 15:34:19 +0000 (+0200)
Subject: Actually prefer /dev/full over /dev/null as a replacement for stdin
X-Git-Tag: release_1_34~9
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=e4d1edadefdeefcca3b72ec32744c52020fe4642;p=thirdparty%2Ftar.git

Actually prefer /dev/full over /dev/null as a replacement for stdin

* lib/stdopen.c (stdopen): Fix improper condition.
Avoid leaking extra file descriptor.
* src/tar.c (main): Set name of the stdout for diagnostics.
Bail out if stdopen fails.
---

diff --git a/lib/stdopen.c b/lib/stdopen.c
index d9775727..8c891168 100644
--- a/lib/stdopen.c
+++ b/lib/stdopen.c
@@ -52,15 +52,22 @@ stdopen (void)
               static const int contrary_mode[]
                 = { O_WRONLY, O_RDONLY, O_RDONLY };
               int mode = contrary_mode[fd];
-              int new_fd;
+              int new_fd = -1;
               /* Open /dev/null with the contrary mode so that the typical
                  read (stdin) or write (stdout, stderr) operation will fail.
                  With descriptor 0, we can do even better on systems that
                  have /dev/full, by opening that write-only instead of
                  /dev/null.  The only drawback is that a write-provoked
                  failure comes with a misleading errno value, ENOSPC.  */
-              if (mode == O_RDONLY
-                  || (new_fd = open ("/dev/full", mode) != fd))
+              if (mode == O_WRONLY)
+		{
+		  if ((new_fd = open ("/dev/full", mode)) != fd)
+		    {
+		      close (new_fd);
+		      new_fd = -1;
+		    }
+		}
+	      if (new_fd == -1)
                 new_fd = open ("/dev/null", mode);
               if (new_fd != fd)
                 {
diff --git a/src/tar.c b/src/tar.c
index 728e38bc..61d77c3d 100644
--- a/src/tar.c
+++ b/src/tar.c
@@ -2751,8 +2751,11 @@ main (int argc, char **argv)
 
   set_quoting_style (0, DEFAULT_QUOTING_STYLE);
 
+  close_stdout_set_file_name (_("stdout"));
   /* Make sure we have first three descriptors available */
-  stdopen ();
+  if (!stdopen ())
+    FATAL_ERROR ((0, errno, "%s",
+		  _("failed to ensure first three descriptors are available")));
 
   /* Pre-allocate a few structures.  */