From: Vivek Goyal <vgoyal@redhat.com>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 09/35] ovl: stack file ops
Date: Thu, 26 Apr 2018 10:13:37 -0400 [thread overview]
Message-ID: <20180426141337.GA4308@redhat.com> (raw)
In-Reply-To: <20180412150826.20988-10-mszeredi@redhat.com>
On Thu, Apr 12, 2018 at 05:08:00PM +0200, Miklos Szeredi wrote:
[..]
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> new file mode 100644
> index 000000000000..a0b606885c41
> --- /dev/null
> +++ b/fs/overlayfs/file.c
> @@ -0,0 +1,76 @@
> +/*
> + * Copyright (C) 2017 Red Hat, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/cred.h>
> +#include <linux/file.h>
> +#include <linux/xattr.h>
> +#include "overlayfs.h"
> +
> +static struct file *ovl_open_realfile(const struct file *file)
> +{
> + struct inode *inode = file_inode(file);
> + struct inode *upperinode = ovl_inode_upper(inode);
> + struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
> + struct file *realfile;
> + const struct cred *old_cred;
> +
> + old_cred = ovl_override_creds(inode->i_sb);
> + realfile = path_open(&file->f_path, file->f_flags | O_NOATIME,
> + realinode, current_cred(), false);
> + revert_creds(old_cred);
> +
> + pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
> + file, file, upperinode ? 'u' : 'l', file->f_flags,
> + realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
> +
> + return realfile;
> +}
> +
> +static int ovl_open(struct inode *inode, struct file *file)
> +{
> + struct dentry *dentry = file_dentry(file);
Hi Miklos,
There is one thing I can't wrap my head around, so I better ask.
file_dentry() will call ovl_d_real() and try to find dentry based on
inode installed in f->f_inode. If ovl_d_real() can't find inode dentry
matching the passed in inode, it warns.
Assume, I have a stacked overlay configuration. Let me call top level
overlay layer ovl1 and lower level overlay layer ovl2. Say I open a
file foo.txt. Now ovl_open() in ovl1 decides that realinode is a lower
inode and installs that inode f->f_inode of realfile. (This should be
ovl2 layer inode, let me call it ovl2_inode). Now ovl_open() of ovl2 layer
will be called and it will call file_dentry() and will look for dentry
corresponding to ovl2_inode. I am wondering what if a copy up of foo.txt
was triggered in ovl1 and by the time we called ovl_d_real(dentry,
ovl2_inode), it will start comparing with inode of ovl1_upper and never
find ovl2_inode.
IOW, I am not able to figure out how do we protect agains copy up races
when ovl_open() calls file_dentry().
Thanks
Vivek
next prev parent reply other threads:[~2018-04-26 14:13 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 15:07 [RFC PATCH 00/35] overlayfs: stack file operations Miklos Szeredi
2018-04-12 15:07 ` [RFC PATCH 01/35] vfs: clean up dedup Miklos Szeredi
2018-04-12 16:25 ` Matthew Wilcox
2018-04-12 17:24 ` Miklos Szeredi
2018-04-12 15:07 ` [RFC PATCH 02/35] vfs: add path_open() Miklos Szeredi
2018-04-12 16:38 ` Matthew Wilcox
2018-04-12 15:07 ` [RFC PATCH 03/35] vfs: optionally don't account file in nr_files Miklos Szeredi
2018-04-12 15:07 ` [RFC PATCH 04/35] ovl: copy up times Miklos Szeredi
2018-04-13 8:25 ` Amir Goldstein
2018-04-13 14:23 ` Vivek Goyal
2018-04-12 15:07 ` [RFC PATCH 05/35] ovl: copy up inode flags Miklos Szeredi
2018-04-12 15:07 ` [RFC PATCH 06/35] Revert "Revert "ovl: get_write_access() in truncate"" Miklos Szeredi
2018-04-12 15:07 ` [RFC PATCH 07/35] ovl: copy up file size as well Miklos Szeredi
2018-04-24 18:10 ` Vivek Goyal
2018-04-12 15:07 ` [RFC PATCH 08/35] ovl: deal with overlay files in ovl_d_real() Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 09/35] ovl: stack file ops Miklos Szeredi
2018-04-26 14:13 ` Vivek Goyal [this message]
2018-04-26 14:43 ` Miklos Szeredi
2018-04-26 14:56 ` Vivek Goyal
2018-04-26 15:01 ` Miklos Szeredi
2018-04-26 15:13 ` Vivek Goyal
2018-04-26 15:21 ` Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 10/35] ovl: add helper to return real file Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 11/35] ovl: readd read_iter Miklos Szeredi
2018-04-13 13:35 ` Amir Goldstein
2018-04-12 15:08 ` [RFC PATCH 12/35] ovl: readd write_iter Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 13/35] ovl: readd fsync Miklos Szeredi
2018-04-23 13:36 ` Vivek Goyal
2018-04-23 13:39 ` Miklos Szeredi
2018-04-23 13:53 ` Vivek Goyal
2018-04-23 14:09 ` Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 14/35] ovl: readd mmap Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 15/35] ovl: readd fallocate Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 16/35] ovl: readd lsattr/chattr support Miklos Szeredi
2018-04-13 14:48 ` Amir Goldstein
2018-04-17 19:51 ` Amir Goldstein
2018-04-22 8:35 ` Amir Goldstein
2018-04-22 15:18 ` Amir Goldstein
2018-04-23 10:21 ` Miklos Szeredi
2018-04-23 10:28 ` Miklos Szeredi
2018-04-23 6:11 ` Ritesh Harjani
2018-04-12 15:08 ` [RFC PATCH 17/35] ovl: readd fiemap Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 18/35] ovl: readd O_DIRECT support Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 19/35] ovl: readd reflink/copyfile/dedup support Miklos Szeredi
2018-04-17 20:31 ` Amir Goldstein
2018-04-18 8:39 ` Amir Goldstein
2018-05-03 16:04 ` Miklos Szeredi
2018-05-03 19:48 ` Amir Goldstein
2018-04-12 15:08 ` [RFC PATCH 20/35] vfs: don't open real Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 21/35] vfs: add f_op->pre_mmap() Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 22/35] ovl: copy-up on MAP_SHARED Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 23/35] vfs: simplify dentry_open() Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 24/35] Revert "ovl: fix relatime for directories" Miklos Szeredi
2018-04-13 14:02 ` Amir Goldstein
2018-04-13 15:55 ` Vivek Goyal
2018-04-12 15:08 ` [RFC PATCH 25/35] Revert "vfs: update ovl inode before relatime check" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 26/35] Revert "ovl: fix may_write_real() for overlayfs directories" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 27/35] Revert "ovl: don't allow writing ioctl on lower layer" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 28/35] Revert "vfs: add flags to d_real()" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 29/35] Revert "vfs: do get_write_access() on upper layer of overlayfs" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 30/35] Revert "vfs: make argument of d_real_inode() const" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 31/35] Revert "vfs: add d_real_inode() helper" Miklos Szeredi
2018-04-18 8:19 ` Amir Goldstein
2018-04-18 11:42 ` Miklos Szeredi
2018-04-18 13:38 ` Steven Rostedt
2018-04-18 13:49 ` Miklos Szeredi
2018-04-18 13:56 ` Steven Rostedt
2018-04-19 19:54 ` Vivek Goyal
2018-04-20 9:14 ` Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 32/35] Partially revert "locks: fix file locking on overlayfs" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 33/35] Revert "fsnotify: support overlayfs" Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 34/35] vfs: simplify d_op->d_real() Miklos Szeredi
2018-04-12 15:08 ` [RFC PATCH 35/35] ovl: fix documentation of non-standard behavior Miklos Szeredi
2018-04-13 11:23 ` Amir Goldstein
2018-04-25 14:49 ` [RFC PATCH 00/35] overlayfs: stack file operations J. R. Okajima
2018-04-25 19:44 ` Miklos Szeredi
2018-05-04 15:23 ` Miklos Szeredi
2018-05-05 16:37 ` Amir Goldstein
2018-05-08 14:25 ` Miklos Szeredi
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=20180426141337.GA4308@redhat.com \
--to=vgoyal@redhat.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=mszeredi@redhat.com \
/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).