Subject: bug#21790: [PATCH] coreutils/cp: handle EOF extents correctly

From: Dmitry Monakhov <[email-masked]>
Date: Fri, 30 Oct 2015 13:02:39 +0400

fallocate can allocate extens beyond EOF via FALLOC_FL_KEEP_SIZE.
Currenly sparse engine tries to copy such extents which is wrong and
result in silent data corruption (leave file with incorrect size).

##TESTCASE
echo blabla > sparse_falloc.in
truncate -s 2M sparse_falloc.in
fallocate -n -o 4M -l 1M sparse_falloc.in
cp sparse_falloc.in sparse_falloc.out
cmp sparse_falloc.in sparse_falloc.out

Signed-off-by: Dmitry Monakhov <[email-masked]>
---
 src/copy.c                   |  7 ++++++-
 tests/cp/sparse-unwritten.sh | 29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100755 tests/cp/sparse-unwritten.sh

diff --git a/src/copy.c b/src/copy.c
index edf022e..de197a4 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -430,7 +430,12 @@ extent_copy (int src_fd, int dest_fd, char *buf, size_t buf_size,
               ext_start = last_ext_start + scan.ext_info[i].ext_length;
               ext_len = 0;
             }
-
+	  /* Is this extent beyond EOF? */
+	  if (ext_start + ext_len >= src_total_size)
+	    {
+	      wrote_hole_at_eof = true;
+	      break;
+	    }
           ext_hole_size = ext_start - last_ext_start - last_ext_len;
 
           wrote_hole_at_eof = false;
diff --git a/tests/cp/sparse-unwritten.sh b/tests/cp/sparse-unwritten.sh
new file mode 100755
index 0000000..4666535
--- /dev/null
+++ b/tests/cp/sparse-unwritten.sh
@@ -0,0 +1,29 @@
+#!/bin/sh
+# Test cp for a file which has extents beyond EOF
+
+# Copyright (C) 2006-2015 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cp
+require_sparse_support_
+
+echo blabla > sparse_falloc.in || framework_failure_
+truncate -s 2M sparse_falloc.in || framework_failure_
+fallocate -n -o 4M -l 1M sparse_falloc.in || framework_failure_
+cp sparse_falloc.in sparse_falloc.out || fail=1
+cmp sparse_falloc.in sparse_falloc.out || fail=1
+
+Exit $fail
-- 
2.1.4