From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Tim Schumacher <timschumi@gmx.de>, Duy Nguyen <pclouds@gmail.com>
Subject: Re: [PATCH] alias: detect loops in mixed execution mode
Date: Fri, 26 Oct 2018 14:44:05 +0200 [thread overview]
Message-ID: <87sh0slvxm.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <20181026083905.GA1705@sigill.intra.peff.net>
On Fri, Oct 26 2018, Jeff King wrote:
> On Sat, Oct 20, 2018 at 02:58:53PM -0400, Jeff King wrote:
>
>> On Sat, Oct 20, 2018 at 01:14:28PM +0200, Ævar Arnfjörð Bjarmason wrote:
>>
>> > > I'd guess this sort of thing is pretty rare. But I wonder if we're
>> > > crossing the line of trying to assume too much about what the user's
>> > > arbitrary code does.
>> > >
>> > > A simple depth counter can limit the fork bomb, and with a high enough
>> > > depth would be unlikely to trigger a false positive. It could also
>> > > protect non-aliases more reasonably, too (e.g., if you have a 1000-deep
>> > > git process hierarchy, there's a good chance you've found an infinite
>> > > loop in git itself).
>> >
>> > I don't think this edge case you're describing is very plausible, and I
>> > doubt it exists in the wild.
>> >
>> > But going by my personal incredulity and a git release breaking code in
>> > the wild would suck, so agree that I need to re-roll this to anticipate
>> > that.
>>
>> I agree it's probably quite rare, if it exists at all. But I also wonder
>> how important looping alias protection is. It's also rare, and the
>> outcome is usually "gee, I wonder why this is taking so long? ^C".
>
> Hmph. So I was speaking before purely hypothetically, but now that your
> patch is in 'next', it is part of my daily build. And indeed, I hit a
> false positive within 5 minutes of building it. ;)
>
> I have an alias like this:
>
> $ git help dotgit
> 'dotgit' is aliased to '!git rev-parse 2>/dev/null || cd ~/compile/git; git'
>
> The idea being that I can run "git dotgit foo" to run "git foo" in the
> current directory, or if it is not a git repository, in my checkout of
> git.git.
>
> I use it in two ways:
>
> - some of my aliases know about it themselves. So I have an alias "ll"
> that does:
>
> $ git help ll
> 'll' is aliased to '!git dotgit --no-pager log --no-walk=unsorted --format='%h (%s, %ad)' --date=short'
>
> with the idea being to produce a nice annotation for a commit id.
> Using "git dotgit" there lets me just run it from any directory,
> since 99% of the time I am working on git.git anyway.
>
> - I have a vim command defined:
>
> command! -nargs=* Git :call MaybeInlineCommand("git dotgit <args>")
>
> so I can do ":Git foo" inside vim and it uses either the current
> repo (e.g., if I'm writing a commit message) or git.git (e.g., if
> I'm writing an email and didn't start in the repo).
>
> So of course the alias expansion is something like (in older versions of
> Git):
>
> 1. "git dotgit ll" runs the dotgit alias, which sees that we need to go
> to the git.git checkout
>
> 2. that runs "git ll"
>
> 3. that runs "git dotgit log"; this second dotgit invocation sees we're
> already in a repository and is a noop
>
> 4. git-log runs
>
> With your patch, step 3 complains:
>
> $ git dotgit ll
> fatal: alias loop detected: expansion of 'dotgit' does not terminate:
> dotgit <==
> ll ==>
>
> So I would really prefer a depth counter that can be set sufficiently
> high to make this case work. ;)
>
>
> As an aside, I got to experience this error message as an unsuspecting
> user would. Unfortunately the output was not super helpful for figuring
> out the cause. I scratched my head for a while before remembering that
> "ll" uses "dotgit" explicitly (which was quite apparent when running
> GIT_TRACE=1, or "git help ll"). I think showing the alias definitions in
> the loop output would have made it much more obvious (if perhaps a bit
> uglier). E.g., something like:
>
> fatal: alias loop...
> ==> dotgit is aliased to '!git rev-parse ...'
> <== ll is aliased to '!git dotgit ...'
>
> -Peff
Yikes.
Junio: After your previous "What's cooking" in
<xmqq8t2u1nkh.fsf@gitster-ct.c.googlers.com> I sent
<87ftx0dg4r.fsf@evledraar.gmail.com>, but should have just replied to
"What's cooking".
I.e. I think this topic should just be ejected, I'll try to submit a
re-roll, but don't know if I have time in the next few days.
Can you please queue a "git revert" of it (or rewind next, but not sure
if you want to do that...).
next prev parent reply other threads:[~2018-10-26 12:44 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-05 8:54 [RFC PATCH v2] Allow aliases that include other aliases Tim Schumacher
2018-09-05 15:48 ` Duy Nguyen
2018-09-05 19:02 ` Tim Schumacher
2018-09-05 17:12 ` Junio C Hamano
2018-09-05 19:12 ` Tim Schumacher
2018-09-05 17:34 ` Jeff King
2018-09-05 20:02 ` Tim Schumacher
2018-09-06 13:38 ` Ævar Arnfjörð Bjarmason
2018-09-06 14:17 ` Ævar Arnfjörð Bjarmason
2018-10-18 22:57 ` [PATCH] alias: detect loops in mixed execution mode Ævar Arnfjörð Bjarmason
2018-10-19 8:28 ` Ævar Arnfjörð Bjarmason
2018-10-19 22:09 ` Jeff King
2018-10-20 10:52 ` Ævar Arnfjörð Bjarmason
2018-10-19 22:07 ` Jeff King
2018-10-20 11:14 ` Ævar Arnfjörð Bjarmason
2018-10-20 18:58 ` Jeff King
2018-10-20 19:18 ` Ævar Arnfjörð Bjarmason
2018-10-22 21:15 ` Jeff King
2018-10-22 21:28 ` Ævar Arnfjörð Bjarmason
2018-10-22 1:23 ` Junio C Hamano
2018-10-26 8:39 ` Jeff King
2018-10-26 12:44 ` Ævar Arnfjörð Bjarmason [this message]
2018-10-29 3:44 ` Junio C Hamano
2018-10-29 14:17 ` Jeff King
2018-09-05 21:51 ` [RFC PATCH v2] Allow aliases that include other aliases Junio C Hamano
2018-09-06 10:16 ` [PATCH v3] " Tim Schumacher
2018-09-06 14:01 ` Ævar Arnfjörð Bjarmason
2018-09-06 14:57 ` Jeff King
2018-09-06 15:10 ` Ævar Arnfjörð Bjarmason
2018-09-06 16:18 ` Jeff King
2018-09-06 19:05 ` Tim Schumacher
2018-09-06 19:17 ` Jeff King
2018-09-06 14:59 ` Jeff King
2018-09-06 18:40 ` Junio C Hamano
2018-09-06 19:05 ` Jeff King
2018-09-06 19:31 ` Tim Schumacher
2018-09-07 22:44 ` [RFC PATCH v4 1/3] Add support for nested aliases Tim Schumacher
2018-09-07 22:44 ` [RFC PATCH v4 2/3] Show the call history when an alias is looping Tim Schumacher
2018-09-08 13:34 ` Duy Nguyen
2018-09-08 16:29 ` Jeff King
2018-09-07 22:44 ` [RFC PATCH v4 3/3] t0014: Introduce alias testing suite Tim Schumacher
2018-09-07 23:38 ` Eric Sunshine
2018-09-14 23:12 ` Tim Schumacher
2018-09-16 7:21 ` Eric Sunshine
2018-09-08 13:28 ` [RFC PATCH v4 1/3] Add support for nested aliases Duy Nguyen
2018-09-16 7:46 ` Tim Schumacher
2018-09-17 15:37 ` Junio C Hamano
2018-09-21 12:45 ` Tim Schumacher
2018-09-21 15:59 ` Junio C Hamano
2018-09-16 7:50 ` [PATCH v5 " Tim Schumacher
2018-09-16 7:50 ` [PATCH v5 2/3] Show the call history when an alias is looping Tim Schumacher
2018-09-16 7:50 ` [PATCH v5 3/3] t0014: Introduce an alias testing suite Tim Schumacher
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