Fix bug #48180: find: avoid segfault for internal '-noop' option

The pseudo-option '-noop' was never meant to be exposed to the user
interface.  If specified by the user, find(1) segfaulted.
Bug introduced in commit FINDUTILS_4_3_0-1-12-g6b8a4db.

* find/parser.c (struct parser_table): Rename the parser_name element of
the ARG_NOOP entry from 'noop' to '--noop', thus indicating its pure
internal character.
(found_parser): Return NULL when the user has passed the '---noop' option;
the caller does the error handling.
* find/testsuite/sv-48180-refuse-noop.sh: Add test.
* find/testsuite/Makefile.am (test_shell_progs): Reference the test.
* NEWS (Bug fixes): Document the fix.

Reported by Tavian Barnes <tavianator@tavianator.com> in
    https://savannah.gnu.org/bugs/?48180

NEWS

@@ -34,6 +34,9 @@ of the - yet more portable - '( -type l -o -type d )'.
 
 ** Bug Fixes
 
+#48180: find -noop (an internal option not intended to be exposed to the user)
+         no longer crashes.  Bug introduced in FINDUTILS-4.3.1.
+
 #48030: find -exec + does not pass all arguments for certain specific filename
         lengths.  After the internal (usually 128k) buffer is full and find(1)
         executed the given command with these arguments, it would miss to run

find/parser.c

@@ -323,7 +323,8 @@ static struct parser_table const parse_table[] =
    */
   {ARG_TEST, "false",                 parse_false,   pred_false}, /* GNU */
   {ARG_TEST, "true",                  parse_true,    pred_true }, /* GNU */
-  {ARG_NOOP, "noop",                  NULL,          pred_true }, /* GNU, internal use only */
+  /* Internal pseudo-option, therefore 3 minus: ---noop.  */
+  {ARG_NOOP, "--noop",                NULL,          pred_true }, /* GNU, internal use only */
 
   /* Various other cases that don't fit neatly into our macro scheme. */
   {ARG_TEST, "help",                  parse_help,    NULL},       /* GNU */
@@ -599,6 +600,9 @@ found_parser (const char *original_arg, const struct parser_table *entry)
    */
   if (entry->type != ARG_POSITIONAL_OPTION)
     {
+      if (entry->type == ARG_NOOP)
+        return NULL;  /* internal use only, trap -noop here.  */
+
       /* Something other than -follow/-daystart.
        * If this is an option, check if it followed
        * a non-option and if so, issue a warning.

find/testsuite/Makefile.am

@@ -260,7 +260,8 @@ test_inode.sh \
 test_type-list.sh \
 sv-34079.sh \
 sv-34976-execdir-fd-leak.sh \
-sv-48030-exec-plus-bug.sh
+sv-48030-exec-plus-bug.sh \
+sv-48180-refuse-noop.sh
 
 EXTRA_DIST = $(EXTRA_DIST_EXP) $(EXTRA_DIST_XO) $(EXTRA_DIST_GOLDEN) \
 	$(test_shell_progs) binary_locations.sh checklists.py

find/testsuite/sv-48180-refuse-noop.sh

@@ -0,0 +1,117 @@
+#! /bin/sh
+# Copyright (C) 2016 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/>.
+#
+
+# This test verifies that find refuses the internal -noop, ---noop option.
+# Between findutils-4.3.1 and 4.6, find dumped core ($? = 139).
+
+testname="$(basename $0)"
+
+. "${srcdir}"/binary_locations.sh
+
+die() {
+  echo "$@" >&2
+  exit 1
+}
+
+# This is used to simplify checking of the return value
+# which is useful when ensuring a command fails as desired.
+# I.e., just doing `command ... &&fail=1` will not catch
+# a segfault in command for example.  With this helper you
+# instead check an explicit exit code like
+#   returns_ 1 command ... || fail
+returns_ () {
+  # Disable tracing so it doesn't interfere with stderr of the wrapped command
+  { set +x; } 2>/dev/null
+
+  local exp_exit="$1"
+  shift
+  "$@"
+  test $? -eq $exp_exit && ret_=0 || ret_=1
+
+  set -x
+  { return $ret_; } 2>/dev/null
+}
+
+# Define the nicest compare available (borrowed from gnulib).
+if diff_out_=`exec 2>/dev/null; diff -u "$0" "$0" < /dev/null` \
+   && diff -u Makefile "$0" 2>/dev/null | grep '^[+]#!' >/dev/null; then
+  # diff accepts the -u option and does not (like AIX 7 'diff') produce an
+  # extra space on column 1 of every content line.
+  if test -z "$diff_out_"; then
+    compare () { diff -u "$@"; }
+  else
+    compare ()
+    {
+      if diff -u "$@" > diff.out; then
+        # No differences were found, but Solaris 'diff' produces output
+        # "No differences encountered". Hide this output.
+        rm -f diff.out
+        true
+      else
+        cat diff.out
+        rm -f diff.out
+        false
+      fi
+    }
+  fi
+elif diff_out_=`exec 2>/dev/null; diff -c "$0" "$0" < /dev/null`; then
+  if test -z "$diff_out_"; then
+    compare () { diff -c "$@"; }
+  else
+    compare ()
+    {
+      if diff -c "$@" > diff.out; then
+        # No differences were found, but AIX and HP-UX 'diff' produce output
+        # "No differences encountered" or "There are no differences between the
+        # files.". Hide this output.
+        rm -f diff.out
+        true
+      else
+        cat diff.out
+        rm -f diff.out
+        false
+      fi
+    }
+  fi
+elif cmp -s /dev/null /dev/null 2>/dev/null; then
+  compare () { cmp -s "$@"; }
+else
+  compare () { cmp "$@"; }
+fi
+
+set -x
+tmpdir="$(mktemp -d)" \
+  && cd "$tmpdir" \
+  || die "FAIL: failed to set up the test in ${tmpdir}"
+
+fail=0
+# Exercise both the previous name of the pseudo-option '-noop',
+# and the now renamed '---noop' option for both find executables.
+for exe in "${ftsfind}" "${oldfind}"; do
+  for opt in 'noop' '--noop'; do
+    out="${exe}${opt}.out"
+    err="${exe}${opt}.err"
+    returns_ 1 "$exe" "-${opt}" >"$out" 2> "$err" || fail=1
+    compare /dev/null "$out" || fail=1
+    grep "find: unknown predicate .-${opt}." "$err" \
+      || { cat "$err"; fail=1; }
+  done
+done
+
+cd ..
+rm -rf "$tmpdir" || exit 1
+exit $fail