Tobias Stoeckmann wrote:
I don't see the need to adjust anything except avoiding this special value. I doubt that anyone ever needed these large numbers.
Yes, it's hard to imagine anyone needing a tabsize that large. Still, the GNU policy is to avoid unnecessary limits, so it's better to make the limit as large as easily possible, which here would be SIZE_MAX - GUTTER_WIDTH_MINIMUM. Also, I see there are other ways the nearby code can overflow. Plus, we should put in a test case for this bug. So I installed the attached patch, which should address these issues. Thanks for reporting the problem.
From 952a704d6b81f5283ec2cede4b9995f04494e1ad Mon Sep 17 00:00:00 2001 From: Paul Eggert <[email protected]> Date: Mon, 27 Oct 2014 19:53:08 -0700 Subject: [PATCH] diff: fix integer overflow problem with --tabsize Reported by Tobias Stoeckmann in: http://bugs.gnu.org/18857 * src/diff.c (main): Don't overflow if INTMAX_MAX / 2 < tabsize. * tests/bignum: New file, to test for this bug. * tests/Makefile.am (TESTS): Add it. --- src/diff.c | 15 ++++++++++----- tests/Makefile.am | 1 + tests/bignum | 14 ++++++++++++++ 3 files changed, 25 insertions(+), 5 deletions(-) create mode 100755 tests/bignum diff --git a/src/diff.c b/src/diff.c index 397815e..03f8e4f 100644 --- a/src/diff.c +++ b/src/diff.c @@ -595,7 +595,8 @@ main (int argc, char **argv) case TABSIZE_OPTION: numval = strtoumax (optarg, &numend, 10); - if (! (0 < numval && numval <= SIZE_MAX) || *numend) + if (! (0 < numval && numval <= SIZE_MAX - GUTTER_WIDTH_MINIMUM) + || *numend) try_help ("invalid tabsize '%s'", optarg); if (tabsize != numval) { @@ -682,10 +683,14 @@ main (int argc, char **argv) a half line plus a gutter is an integral number of tabs, so that tabs in the right column line up. */ - intmax_t t = expand_tabs ? 1 : tabsize; - intmax_t w = width; - intmax_t off = (w + t + GUTTER_WIDTH_MINIMUM) / (2 * t) * t; - sdiff_half_width = MAX (0, MIN (off - GUTTER_WIDTH_MINIMUM, w - off)), + size_t t = expand_tabs ? 1 : tabsize; + size_t w = width; + size_t t_plus_g = t + GUTTER_WIDTH_MINIMUM; + size_t unaligned_off = (w >> 1) + (t_plus_g >> 1) + (w & t_plus_g & 1); + size_t off = unaligned_off - unaligned_off % t; + sdiff_half_width = (off <= GUTTER_WIDTH_MINIMUM || w <= off + ? 0 + : MIN (off - GUTTER_WIDTH_MINIMUM, w - off)); sdiff_column2_offset = sdiff_half_width ? off : w; } diff --git a/tests/Makefile.am b/tests/Makefile.am index 005d9f0..438fbdf 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -2,6 +2,7 @@ TESTS = \ basic \ + bignum \ binary \ colliding-file-names \ excess-slash \ diff --git a/tests/bignum b/tests/bignum new file mode 100755 index 0000000..a0c95f6 --- /dev/null +++ b/tests/bignum @@ -0,0 +1,14 @@ +#!/bin/sh +# big numbers + +. "${srcdir=.}/init.sh"; path_prepend_ ../src + +fail=0 + +for tabsize in 2147483648 9223372036854775808; do + diff --tabsize=$tabsize /dev/null /dev/null + status=$? + test $status -eq 0 || test $status -eq 2 || fail=1 +done + +Exit $fail -- 1.9.3
