From 886a0e4986628488e9a711b576296f8be58a8b19 Mon Sep 17 00:00:00 2001
From: Colin Walters <walters@verbum.org>
Date: Tue, 9 Oct 2018 13:30:54 +0000
Subject: [PATCH] composeutil: Test for ability to open new /dev/null

If `nodev` is set, we should fail fast.  See also
https://github.com/containers/storage/pull/208

Closes: #1604
Approved by: jlebon
---
 src/app/rpmostree-composeutil.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/app/rpmostree-composeutil.c b/src/app/rpmostree-composeutil.c
index 0a64b9f4..a2704f45 100644
--- a/src/app/rpmostree-composeutil.c
+++ b/src/app/rpmostree-composeutil.c
@@ -131,6 +131,16 @@ rpmostree_composeutil_legacy_prep_dev (int         rootfs_dfd,
         return glnx_throw_errno (error);
     }
 
+  { GLNX_AUTO_PREFIX_ERROR ("Testing /dev/null in target root (is nodev set?)", error);
+    glnx_autofd int devnull_fd = -1;
+    if (!glnx_openat_rdonly (dest_fd, "null", TRUE, &devnull_fd, error))
+      return FALSE;
+    char buf[1];
+    ssize_t s = read (devnull_fd, buf, sizeof (buf));
+    if (s < 0)
+      return glnx_throw_errno_prefix (error, "read");
+  }
+
   return TRUE;
 }