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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
	Jeff King <peff@peff.net>, Erik Faye-Lund <kusmabite@gmail.com>,
	Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [RFC PATCH 00/10] range-diff: fix segfault due to integer overflow
Date: Fri, 10 Dec 2021 16:07:15 +0100	[thread overview]
Message-ID: <211210.864k7gcx3r.gmgdl@evledraar.gmail.com> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.2112101528200.90@tvgsbejvaqbjf.bet>


On Fri, Dec 10 2021, Johannes Schindelin wrote:

> Hi Ævar,
>
> On Thu, 9 Dec 2021, Ævar Arnfjörð Bjarmason wrote:
>
>> The difference between "master" and "git-for-windows/main" is large
>> enough that comparing the two will segfault on my system. This is
>> because the range-diff code does some expensive calculations and will
>> overflow the "int" type.
>
> You are holding this thing wrong.
>
> The `main` branch of Git for Windows uses merging rebases, therefore you
> need to use a commit range like
> `git-for-windows/main^{/^Start.the.merging}..git-for-windows/main` and
> compare it to `git-for-windows/main..master`.
>
> Failing that, you will receive only bogus results.

Indeed. FWIW I got this segfault on an actual local range-diff that's
useful for a very large range & started digging.

I then tried to come up with some arbitrary command someone with a
git.git clone might be able to run that would reproduce it without
having to tell them to clone chromium.git or <other very large repo>.

> As to the patch series, it likely does the wrong thing. Just like we error
> out on insanely large input in libxdiff, `range-diff` should do the same.

I haven't come up with an actual use-case for diffing something large
(maybe someone storing DNA sequences as text would?), but have run into
practical cases where range-diff would be useful on range where it
currently segfaults. E.g. repos that get 500-1000 commits/day someone
cherry-picks commits between branches & rewords/adjusts, and you're
trying to range-diff it 2 months later looking for differences...

  reply	other threads:[~2021-12-10 15:13 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-09 19:19 [RFC PATCH 00/10] range-diff: fix segfault due to integer overflow Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 01/10] string-list API: change "nr" and "alloc" to "size_t" Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 02/10] range-diff.c: don't use st_mult() for signed "int" Ævar Arnfjörð Bjarmason
2021-12-10  3:39   ` Jeff King
2021-12-10 10:22     ` Ævar Arnfjörð Bjarmason
2021-12-10 11:41       ` Jeff King
2021-12-10 12:31         ` Ævar Arnfjörð Bjarmason
2021-12-10 19:24           ` Phillip Wood
2021-12-14 14:34           ` Jeff King
2021-12-10 14:27         ` Johannes Schindelin
2021-12-10 14:58           ` Ævar Arnfjörð Bjarmason
2021-12-11 14:01             ` Johannes Schindelin
2021-12-12 17:44               ` Ævar Arnfjörð Bjarmason
2021-12-14 14:42           ` Jeff King
2021-12-09 19:19 ` [RFC PATCH 03/10] range-diff.c: use "size_t" to refer to "struct string_list"'s "nr" Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 04/10] range-diff: zero out elements in "cost" first Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 05/10] linear-assignment.c: split up compute_assignment() function Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 06/10] linear-assignment.c: take "size_t", not "int" for *_count Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 07/10] linear-assignment.c: convert a macro to a "static inline" function Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 08/10] linear-assignment.c: detect signed add/mul on GCC and Clang Ævar Arnfjörð Bjarmason
2021-12-10  3:56   ` Jeff King
2021-12-09 19:19 ` [RFC PATCH 09/10] linear-assignment.c: add and use intprops.h from Gnulib Ævar Arnfjörð Bjarmason
2021-12-09 19:19 ` [RFC PATCH 10/10] linear-assignment.c: use "intmax_t" instead of "int" Ævar Arnfjörð Bjarmason
2021-12-10  4:00   ` Jeff King
2021-12-10 12:30 ` [RFC PATCH v2 0/5] range-diff: fix segfault due to integer overflow Ævar Arnfjörð Bjarmason
2021-12-10 12:30   ` [RFC PATCH v2 1/5] range-diff: zero out elements in "cost" first Ævar Arnfjörð Bjarmason
2021-12-14 13:36     ` Jeff King
2021-12-10 12:30   ` [RFC PATCH v2 2/5] linear-assignment.c: split up compute_assignment() function Ævar Arnfjörð Bjarmason
2021-12-14 13:39     ` Jeff King
2021-12-10 12:30   ` [RFC PATCH v2 3/5] linear-assignment.c: take "size_t", not "int" for *_count Ævar Arnfjörð Bjarmason
2021-12-14 13:40     ` Jeff King
2021-12-10 12:30   ` [RFC PATCH v2 4/5] range-diff.c: rename "n" to "column_count" in get_correspondences() Ævar Arnfjörð Bjarmason
2021-12-14 13:42     ` Jeff King
2021-12-10 12:30   ` [RFC PATCH v2 5/5] range-diff: fix integer overflow & segfault on cost[i + n * j] Ævar Arnfjörð Bjarmason
2021-12-14 14:04     ` Jeff King
2021-12-10 14:31 ` [RFC PATCH 00/10] range-diff: fix segfault due to integer overflow Johannes Schindelin
2021-12-10 15:07   ` Ævar Arnfjörð Bjarmason [this message]
2021-12-21 23:22   ` Philip Oakley
2021-12-21 23:36     ` Ævar Arnfjörð Bjarmason
2021-12-22 20:50       ` Johannes Schindelin
2021-12-22 21:11         ` Jeff King
2021-12-24 11:15       ` Philip Oakley
2021-12-24 16:46         ` Ævar Arnfjörð Bjarmason
2021-12-24 18:31           ` Philip Oakley

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