From: Jeff King <peff@peff.net>
To: Mike Hommey <mh@glandium.org>
Cc: "Johannes Sixt" <j6t@kdbg.org>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
git@vger.kernel.org
Subject: Re: Closing fds twice when using remote helpers
Date: Wed, 15 May 2019 19:53:40 -0400 [thread overview]
Message-ID: <20190515235339.GA3579@sigill.intra.peff.net> (raw)
In-Reply-To: <20190515220834.svurujspjt3bmath@glandium.org>
On Thu, May 16, 2019 at 07:08:34AM +0900, Mike Hommey wrote:
> > >> - Except, well, fds being what they are, we in fact just closed a fd
> > >> from a packed_git->pack_fd. So, when use_pack is later called, and
> > >> tries to mmap data from that pack, it fails because the file
> > >> descriptor was closed.
> >
> > Either dup() the file descriptor, or mmap() before you call the
> > consuming start_command().
If I understand your case correctly, the mmap() is not relevant. The
issue is that we close a random file descriptor accidentally, and it
just happens to be a pack descriptor later on. Right?
> You seem to imply this is my code doing something. It's not. The process
> that is doing all the things I noted above is an unmodified `git fetch`,
> when using a remote-helper transport. The use_pack happens after the
> transport is disposed because that's at the end of git fetch, when it
> updates refs.
Yes, it's a bug in git.
> Anyway, it would seem the fix is to dup(out) when passing it as in to
> start_command?
Generally, yes. It looks like maybe this spot?
diff --git a/transport-helper.c b/transport-helper.c
index fcd2a58d0e..45cdf891ec 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -433,7 +433,7 @@ static int get_importer(struct transport *transport, struct child_process *fasti
struct helper_data *data = transport->data;
int cat_blob_fd, code;
child_process_init(fastimport);
- fastimport->in = helper->out;
+ fastimport->in = xdup(helper->out);
argv_array_push(&fastimport->args, "fast-import");
argv_array_push(&fastimport->args, debug ? "--stats" : "--quiet");
One thing I'd wonder, though: what is the contract between the helper
and fast-import here? In the current code, when the helper closes its
stdout, fast-import will see EOF. But not if we are holding on to
another copy of the descriptor.
In that case, the right solution is probably more like:
fastimport->in = helper->out;
helper->out = -1; /* hand ownership to fast-import */
-Peff
next prev parent reply other threads:[~2019-05-16 1:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-15 10:56 Closing fds twice when using remote helpers Mike Hommey
2019-05-15 11:43 ` Ævar Arnfjörð Bjarmason
2019-05-15 17:59 ` Johannes Sixt
2019-05-15 22:08 ` Mike Hommey
2019-05-15 23:53 ` Jeff King [this message]
2019-05-16 0:48 ` Mike Hommey
2019-05-16 3:28 ` Jeff King
2019-05-16 8:35 ` Mike Hommey
2019-05-16 21:47 ` Jeff King
2019-05-16 22:02 ` Mike Hommey
2019-05-16 0:31 ` Mike Hommey
2019-05-16 0:37 ` [PATCH 1/2] dup() the input fd for fast-import used for " Mike Hommey
2019-05-16 0:37 ` [PATCH 2/2] Use xmmap_gently instead of xmmap in use_pack Mike Hommey
2019-05-16 3:34 ` Jeff King
2019-05-16 3:28 ` [PATCH 1/2] dup() the input fd for fast-import used for remote helpers Jeff King
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190515235339.GA3579@sigill.intra.peff.net \
--to=peff@peff.net \
--cc=avarab@gmail.com \
--cc=git@vger.kernel.org \
--cc=j6t@kdbg.org \
--cc=mh@glandium.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).