From: Jann Horn <jannh@google.com>
To: Christian Brauner <christian@brauner.io>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
kernel list <linux-kernel@vger.kernel.org>,
David Howells <dhowells@redhat.com>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
sparclinux@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
Miklos Szeredi <miklos@szeredi.hu>,
the arch/x86 maintainers <x86@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-xtensa@linux-xtensa.org, Todd Kjos <tkjos@android.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-m68k@lists.linux-m68k.org,
Al Viro <viro@zeniv.linux.org.uk>,
Oleg Nesterov <oleg@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Dmitry V. Levin" <ldv@altlinux.org>,
linux-arm-kernel@lists.infradead.org,
Florian Weimer <fweimer@redhat.com>,
linux-parisc@vger.kernel.org,
Linux API <linux-api@vger.kernel.org>,
linux-mips@vger.kernel.org, linux-alpha@vger.kernel.org,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v1 1/2] open: add close_range()
Date: Thu, 23 May 2019 16:32:14 +0200 [thread overview]
Message-ID: <CAG48ez0Uq2GQnQsuPkNrDdJVku_6GPeZ_5F_-5J3iy2CULr0_Q@mail.gmail.com> (raw)
In-Reply-To: <20190523115118.pmscbd6kaqy37dym@brauner.io>
On Thu, May 23, 2019 at 1:51 PM Christian Brauner <christian@brauner.io> wrote:
[...]
> I kept it dumb and was about to reply that your solution introduces more
> code when it seemed we wanted to keep this very simple for now.
> But then I saw that find_next_opened_fd() already exists as
> find_next_fd(). So it's actually not bad compared to what I sent in v1.
> So - with some small tweaks (need to test it and all now) - how do we
> feel about?:
[...]
> static int __close_next_open_fd(struct files_struct *files, unsigned *curfd, unsigned maxfd)
> {
> struct file *file = NULL;
> unsigned fd;
> struct fdtable *fdt;
>
> spin_lock(&files->file_lock);
> fdt = files_fdtable(files);
> fd = find_next_fd(fdt, *curfd);
find_next_fd() finds free fds, not used ones.
> if (fd >= fdt->max_fds || fd > maxfd)
> goto out_unlock;
>
> file = fdt->fd[fd];
> rcu_assign_pointer(fdt->fd[fd], NULL);
> __put_unused_fd(files, fd);
You can't do __put_unused_fd() if the old pointer in fdt->fd[fd] was
NULL - because that means that the fd has been reserved by another
thread that is about to put a file pointer in there, and if you
release the fd here, that messes up the refcounting (or hits the
BUG_ON() in __fd_install()).
> out_unlock:
> spin_unlock(&files->file_lock);
>
> if (!file)
> return -EBADF;
>
> *curfd = fd;
> filp_close(file, files);
> return 0;
> }
>
> int __close_range(struct files_struct *files, unsigned fd, unsigned max_fd)
> {
> if (fd > max_fd)
> return -EINVAL;
>
> while (fd <= max_fd) {
Note that with a pattern like this, you have to be careful about what
happens if someone gives you max_fd==0xffffffff - then this condition
is always true and the loop can not terminate this way.
> if (__close_next_fd(files, &fd, maxfd))
> break;
(obviously it can still terminate this way)
> cond_resched();
> fd++;
> }
>
> return 0;
> }
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-05-23 14:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 15:52 [PATCH v1 1/2] open: add close_range() Christian Brauner
2019-05-22 15:52 ` [PATCH v1 2/2] tests: add close_range() tests Christian Brauner
2019-05-22 16:57 ` [PATCH v1 1/2] open: add close_range() Oleg Nesterov
2019-05-23 11:51 ` Christian Brauner
2019-05-23 14:14 ` Christian Brauner
2019-05-23 14:28 ` Christian Brauner
2019-05-23 16:21 ` Oleg Nesterov
2019-05-23 14:32 ` Jann Horn [this message]
2019-05-23 14:37 ` Christian Brauner
2019-05-23 16:22 ` Konstantin Khlebnikov
2019-05-23 16:29 ` David Laight
2019-05-23 16:33 ` Christian Brauner
2019-05-24 7:43 ` Arnd Bergmann
2019-05-24 9:57 ` Christian Brauner
2019-05-24 10:31 ` Christian Brauner
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=CAG48ez0Uq2GQnQsuPkNrDdJVku_6GPeZ_5F_-5J3iy2CULr0_Q@mail.gmail.com \
--to=jannh@google.com \
--cc=arnd@arndb.de \
--cc=christian@brauner.io \
--cc=dhowells@redhat.com \
--cc=fweimer@redhat.com \
--cc=ldv@altlinux.org \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-m68k@lists.linux-m68k.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=miklos@szeredi.hu \
--cc=oleg@redhat.com \
--cc=shuah@kernel.org \
--cc=sparclinux@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=tkjos@android.com \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.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.
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).