cp: avoid data-corrupting free-memory-read

* src/extent-scan.c (extent_scan_read): Reset our last_ei
pointer whenever the parent buffer might have just been freed.
* tests/cp/fiemap-extent-FMR.sh: New test.
* tests/local.mk (all_tests): Add it.
* NEWS (Bug fixes): Mention it.
Reported by Mike Gerth in http://bugs.gnu.org/12656, and with
help from Alan Curry.  Bug introduced in commit v8.10-60-g18f5a85.

diff --git a/NEWS b/NEWS
index aff5bf18e95160a7fb0df0ed63ee7fb0a96c547b..0fc2a94d1b3e19dd113333009fa956f29b3de3b0 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,11 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  cp could read from freed memory and could even make corrupt copies.
+  This could happen with a very fragmented and sparse input file,
+  on GNU/Linux file systems supporting fiemap extent scanning.
+  [bug introduced in coreutils-8.11]
+
   cp --no-preserve=mode now no longer preserves the original file's
   permissions but correctly sets mode specified by 0666 & ~umask
 

diff --git a/src/extent-scan.c b/src/extent-scan.c
index 0c25c5705232e25adeb3844fd592909bccdde875..f962298556afc99e28bdf5a8822bd95ed7ea4ab1 100644 (file)
--- a/src/extent-scan.c
+++ b/src/extent-scan.c
@@ -89,7 +89,7 @@ extern bool
 extent_scan_read (struct extent_scan *scan)
 {
   unsigned int si = 0;
-  struct extent_info *last_ei IF_LINT ( = scan->ext_info);
+  struct extent_info *last_ei = scan->ext_info;
 
   while (true)
     {
@@ -127,8 +127,14 @@ extent_scan_read (struct extent_scan *scan)
 
       assert (scan->ei_count <= SIZE_MAX - fiemap->fm_mapped_extents);
       scan->ei_count += fiemap->fm_mapped_extents;
-      scan->ext_info = xnrealloc (scan->ext_info, scan->ei_count,
-                                  sizeof (struct extent_info));
+      {
+        /* last_ei points into a buffer that may be freed via xnrealloc.
+           Record its offset and adjust after allocation.  */
+        size_t prev_idx = last_ei - scan->ext_info;
+        scan->ext_info = xnrealloc (scan->ext_info, scan->ei_count,
+                                    sizeof (struct extent_info));
+        last_ei = scan->ext_info + prev_idx;
+      }
 
       unsigned int i = 0;
       for (i = 0; i < fiemap->fm_mapped_extents; i++)

diff --git a/tests/cp/fiemap-FMR.sh b/tests/cp/fiemap-FMR.sh
new file mode 100755 (executable)
index 0000000..10c9e05
--- /dev/null
+++ b/tests/cp/fiemap-FMR.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+# Trigger a free-memory read bug in cp from coreutils-[8.11..8.19]
+
+# Copyright (C) 2012 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_valgrind_
+require_perl_
+: ${PERL=perl}
+
+$PERL -e 'for (1..600) { sysseek (*STDOUT, 4096, 1)' \
+  -e '&& syswrite (*STDOUT, "a" x 1024) or die "$!"}' > j || fail=1
+valgrind --quiet --error-exitcode=3 cp j j2 || fail=1
+cmp j j2 || fail=1
+
+Exit $fail

diff --git a/tests/local.mk b/tests/local.mk
index 486bf312b70c7c7a03ef35c3b135ac8cf4dd3feb..5a237fa71459d9f681cc94f1eeb076d81d9ec0d5 100644 (file)
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -418,6 +418,7 @@ all_tests =                                 \
   tests/cp/existing-perm-race.sh               \
   tests/cp/fail-perm.sh                                \
   tests/cp/fiemap-empty.sh                     \
+  tests/cp/fiemap-FMR.sh                       \
   tests/cp/fiemap-perf.sh                      \
   tests/cp/fiemap-2.sh                         \
   tests/cp/file-perm-race.sh                   \