From 57ee5493d996b69a02d367829d579729e8b20eaf Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Tue, 27 Sep 2011 16:32:35 +0200 Subject: sort: avoid a NaN-induced infloop These commands would fail to terminate: yes -- -nan | head -156903 | sort -g > /dev/null echo nan > F; sort -m -g F F That can happen with any strtold implementation that includes uninitialized data in its return value. The problem arises in the mergefps function when bubble-sorting the two or more lines, each from one of the input streams being merged: compare(a,b) returns 64, yet compare(b,a) also returns a positive value. With a broken comparison function like that, the bubble sort never terminates. Why do the long-double bit strings corresponding to two identical "nan" strings not compare equal? Because some parts of the result are uninitialized and thus depend on the state of the stack. For more details, see http://bugs.gnu.org/9612. * src/sort.c (nan_compare): New function. (general_numcompare): Use it rather than bare memcmp. Reported by Aaron Denney in http://bugs.debian.org/642557. * NEWS (Bug fixes): Mention it. * tests/misc/sort-NaN-infloop: New file. * tests/Makefile.am (TESTS): Add it. --- tests/misc/sort-NaN-infloop | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) create mode 100755 tests/misc/sort-NaN-infloop (limited to 'tests/misc/sort-NaN-infloop') diff --git a/tests/misc/sort-NaN-infloop b/tests/misc/sort-NaN-infloop new file mode 100755 index 000000000..ead871e43 --- /dev/null +++ b/tests/misc/sort-NaN-infloop @@ -0,0 +1,28 @@ +#!/bin/sh +# exercise the NaN-infloop bug in coreutils-8.13 + +# Copyright (C) 2011 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 . + +. "${srcdir=.}/init.sh"; path_prepend_ ../src +print_ver_ sort + +echo nan > F || fail=1 +printf 'nan\nnan\n' > exp || fail=1 +timeout 10 sort -g -m F F > out || fail=1 + +compare out exp || fail=1 + +Exit $fail -- cgit v1.2.3-54-g00ecf