From 2771d66e4fdb2e2d158d092ead543638115971f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <address@hidden>
Date: Sun, 29 Oct 2017 15:29:05 -0700
Subject: [PATCH] df: fix hang with fifo argument

* src/df.c (main): stat() before open(), and avoid
the optional open when given a fifo argument.
* tests/df/unreadable.sh: Add a test case.
* NEWS: Mention the fix.
Fixes https://bugs.gnu.org/29038
---
 NEWS                   |  3 +++
 src/df.c               | 13 ++++++++-----
 tests/df/unreadable.sh |  3 +++
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/NEWS b/NEWS
index 806e3ef..3e6704d 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   invalidated.  [bug introduced for "direct" in coreutils-7.5,
   and with the "nocache" implementation in coreutils-8.11]
 
+  df no longer hangs when given a fifo argument.
+  [bug introduced in coreutils-7.3]
+
   ptx -S no longer infloops for a pattern which returns zero-length matches.
   [the bug dates back to the initial implementation]
 
diff --git a/src/df.c b/src/df.c
index 7345bc9..ee04d51 100644
--- a/src/df.c
+++ b/src/df.c
@@ -1710,16 +1710,19 @@ main (int argc, char **argv)
         {
           /* Prefer to open with O_NOCTTY and use fstat, but fall back
              on using "stat", in case the file is unreadable.  */
-          int fd = open (argv[i], O_RDONLY | O_NOCTTY);
-          if ((fd < 0 || fstat (fd, &stats[i - optind]))
-              && stat (argv[i], &stats[i - optind]))
+          if (stat (argv[i], &stats[i - optind]))
             {
               error (0, errno, "%s", quotef (argv[i]));
               exit_status = EXIT_FAILURE;
               argv[i] = NULL;
             }
-          if (0 <= fd)
-            close (fd);
+          else if (! S_ISFIFO (stats[i - optind].st_mode))
+            {
+              /* open() is needed to automount in some cases.  */
+              int fd = open (argv[i], O_RDONLY | O_NOCTTY);
+              if (0 <= fd)
+                close (fd);
+            }
         }
     }
 
diff --git a/tests/df/unreadable.sh b/tests/df/unreadable.sh
index c28cdc9..fb4c91c 100755
--- a/tests/df/unreadable.sh
+++ b/tests/df/unreadable.sh
@@ -24,6 +24,9 @@ touch unreadable || fail=1
 chmod a-r unreadable || fail=1
 df unreadable || fail=1
 
+mkfifo_or_skip_ fifo
+timeout 10 df fifo || fail=1
+
 test "$fail" = 1 && dump_mount_list_
 
 Exit $fail
-- 
2.9.3