From: Greg Kurz <groug@kaod.org>
To: Dominique Martinet <asmadeus@codewreck.org>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
v9fs-developer@lists.sourceforge.net,
Latchesar Ionkov <lucho@ionkov.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Eric Van Hensbergen <ericvh@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [V9fs-developer] [PATCH kernel] 9p/trans_fd: Check file mode at opening
Date: Wed, 29 Jul 2020 08:38:22 +0200 [thread overview]
Message-ID: <20200729083822.66e165ed@bahia.lan> (raw)
In-Reply-To: <20200729061449.GA19682@nautica>
On Wed, 29 Jul 2020 08:14:49 +0200
Dominique Martinet <asmadeus@codewreck.org> wrote:
> Greg Kurz wrote on Tue, Jul 28, 2020:
> > > The "fd" transport layer uses 2 file descriptors passed externally
> > > and calls kernel_write()/kernel_read() on these. If files were opened
> > > without FMODE_WRITE/FMODE_READ, WARN_ON_ONCE() will fire.
>
> There already is a fix in linux-next as a39c46067c84 ("net/9p: validate
> fds in p9_fd_open")
>
> > > This adds file mode checking in p9_fd_open; this returns -EBADF to
> > > preserve the original behavior.
> >
> > So this would cause open() to fail with EBADF, which might look a bit
Oops... this seems to rather end up in mount(). :)
> > weird to userspace since it didn't pass an fd... Is this to have a
> > different error than -EIO that is returned when either rfd or wfd
> > doesn't point to an open file descriptor ? If yes, why do we care ?
>
> FWIW the solution taken just returns EIO as it would if an invalid fd
> was given, but since it did pass an fd EBADF actually makes sense to me?
>
POSIX says:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
[EBADF]
Bad file descriptor. A file descriptor argument is out of range, refers to
no open file, or a read (write) request is made to a file that is only open
for writing (reading).
It seems that EBADF would be appropriate for both the existing and the
new error path.
> However to the second question I'm not sure I care :)
>
> > > Found by syzkaller.
>
> I'm starting to understand where David comment came from the other day,
> I guess it's still time to change my mind and submit to linus now I've
> had time to test it...
>
prev parent reply other threads:[~2020-07-29 6:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 12:41 [PATCH kernel] 9p/trans_fd: Check file mode at opening Alexey Kardashevskiy
2020-07-28 17:42 ` [V9fs-developer] " Greg Kurz
2020-07-28 23:50 ` Alexey Kardashevskiy
2020-07-29 6:06 ` Greg Kurz
2020-07-29 6:14 ` Dominique Martinet
2020-07-29 6:38 ` Greg Kurz [this message]
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200729083822.66e165ed@bahia.lan \
--to=groug@kaod.org \
--cc=aik@ozlabs.ru \
--cc=asmadeus@codewreck.org \
--cc=davem@davemloft.net \
--cc=ericvh@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lucho@ionkov.net \
--cc=netdev@vger.kernel.org \
--cc=v9fs-developer@lists.sourceforge.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.
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 NNTP newsgroup(s).