From: "Randall S. Becker" <rsbecker@nexbridge.com>
To: "'Jeff King'" <peff@peff.net>
Cc: <git@vger.kernel.org>
Subject: RE: [Possible Bug] Use of write on size-limited platforms
Date: Mon, 15 Jun 2020 18:38:34 -0400 [thread overview]
Message-ID: <002801d64365$b6fdc2d0$24f94870$@nexbridge.com> (raw)
In-Reply-To: <20200615215937.GA636737@coredump.intra.peff.net>
On June 15, 2020 6:00 PM, Jeff King wrote:
> On Mon, Jun 08, 2020 at 05:41:34PM -0400, Randall S. Becker wrote:
> > I just wanted to check the following calls to make sure that it does
> > not fwrite or write should be xread/xwrite or are guaranteed not to
> > exceed
> > MAX_IO_SIZE:
> >
> > strbuf.c: strbuf_write, strbuf_write_fd, the size is not specified.
> >
> > The other uses of read/write appear to be safe.
>
> strbuf_write() is using fwrite(), and we don't enforce MAX_IO_SIZE with stdio
> anywhere else. And I'd expect in general that if there are any platform
> limitations, the system libc would choose a sane value anyway.
> So that one is probably fine.
>
> I think strbuf_write_fd() is wrong to use a raw write(), but for several
> reasons:
>
> - it won't enforce MAX_IO_SIZE, as you note
>
> - it won't handle EINTR, etc; callers need to be prepared to restart
> such a write
>
> - it won't handle a partial write by looping until all output is sent
>
> For the latter two, there are cases where some callers want the flexibility to
> stop when seeing a signal or a partial write. But I don't think that makes any
> sense for strbuf_write_fd(). If I pass in a strbuf with 8kb of data and I get a
> return value that indicates we only wrote 4kb, what do I do next? I certainly
> can't call strbuf_write_fd() again, since it would write from the beginning of
> the strbuf again. I'd have to call xwrite() myself after that. At which point I
> may as well have done so for the first call. :)
>
> So I think this really ought to be using write_in_full(). There's only one caller,
> and I think it would be improved by the switch. Do you want to write a
> patch?
>
> You could make an argument that the fwrite() version ought to also loop,
> since it's possible to get a partial write there, too. But we don't do that in
> general. I suspect in practice most stdio implementations will keep writing
> until they see an error, and most callers don't bother checking stdio errors at
> all, or use ferror().
I'll give the patch a go. It is very simple. Would you suggest removing the strbuf_write_fd() as part of this patch since it only impacts bugreport.c?
Regards,
Randall
next prev parent reply other threads:[~2020-06-15 22:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-08 21:41 [Possible Bug] Use of write on size-limited platforms Randall S. Becker
2020-06-15 21:59 ` Jeff King
2020-06-15 22:38 ` Randall S. Becker [this message]
2020-06-16 8:02 ` Jeff King
2020-06-19 15:05 ` Randall S. Becker
2020-06-19 19:35 ` Junio C Hamano
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='002801d64365$b6fdc2d0$24f94870$@nexbridge.com' \
--to=rsbecker@nexbridge.com \
--cc=git@vger.kernel.org \
--cc=peff@peff.net \
/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).