linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"#v4 . 16" <stable@vger.kernel.org>
Subject: Re: [PATCH v3 1/4] ovl: use insert_inode_locked4() to hash a newly created inode
Date: Wed, 16 May 2018 10:34:00 +0200	[thread overview]
Message-ID: <CAJfpegtMvjEjC7B4JpnjyYxzbY=pbW_ATKkKCkjKEsQqzxqqNg@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxizDzcH7rDCTGHCpjD90RwKCqcjGCSyXx6GDU7Oj_nc6Q@mail.gmail.com>

On Tue, May 15, 2018 at 3:37 PM, Amir Goldstein <amir73il@gmail.com> wrote:
> On Tue, May 15, 2018 at 4:23 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
>> On Tue, May 15, 2018 at 01:26:09PM +0300, Amir Goldstein wrote:
>>> Currently, there is a small window where ovl_obtain_alias() can
>>> race with ovl_instantiate() and create two different overlay inodes
>>> with the same underlying real non-dir non-hardlink inode.
>>>
>>> The race requires an adversary to guess the file handle of the
>>> yet to be created upper inode and decode the guessed file handle
>>> after ovl_creat_real(), but before ovl_instantiate().
>>>
>>> This patch fixes the race, by using insert_inode_locked4() to add
>>> a newly created inode to icache.
>>>
>>> If the newly created inode apears to already exist in icache (hashed
>>> by the same real upper inode), we export this error to user instead
>>> of silently not hashing the new inode.
>>
>> So we might return an error to user saying operation failed, but still
>> create file on upper. Does that sound little odd?
>>
>
> Yes, but I don't see a better solution.

Might be better to kick the other, offending inode out, instead of
returning an error.  It would also simplify the error handling.

We can do that by creating an ovl_inode_test_kick() variant that
unhashes the inode on match.  Also needs insert_inode_locked4() to use
hlist_for_each_entry_safe() instead of hlist_for_each_entry().

Thanks,
Miklos

  reply	other threads:[~2018-05-16  8:34 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-15 10:26 [PATCH v3 0/4] Overlayfs mkdir related fixes Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 1/4] ovl: use insert_inode_locked4() to hash a newly created inode Amir Goldstein
2018-05-15 13:23   ` Vivek Goyal
2018-05-15 13:37     ` Amir Goldstein
2018-05-16  8:34       ` Miklos Szeredi [this message]
2018-05-16  9:51         ` Amir Goldstein
2018-05-16 10:14           ` Miklos Szeredi
2018-05-16 11:03             ` Amir Goldstein
2018-05-17  6:03       ` Amir Goldstein
2018-05-17  8:10         ` Miklos Szeredi
2018-05-17  8:45           ` Amir Goldstein
2018-05-17  8:53           ` Miklos Szeredi
2018-05-17  8:58             ` Amir Goldstein
2018-05-17  9:07               ` Miklos Szeredi
2018-05-17 16:14                 ` Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 2/4] ovl: relax WARN_ON() real inode attributes mismatch Amir Goldstein
2018-05-15 12:48   ` Vivek Goyal
2018-05-15 12:55     ` Amir Goldstein
2018-05-16 10:29   ` Miklos Szeredi
2018-05-16 11:06     ` Amir Goldstein
2018-05-16 11:18       ` Miklos Szeredi
2018-05-16 13:46         ` Amir Goldstein
2018-05-15 10:26 ` [PATCH v3 3/4] ovl: create helper ovl_create_temp() Amir Goldstein
2018-05-16 10:41   ` Miklos Szeredi
2018-05-16 11:15     ` Amir Goldstein
2018-05-16 11:37       ` Miklos Szeredi
2018-05-15 10:26 ` [PATCH v3 4/4] ovl: make ovl_create_real() cope with vfs_mkdir() safely Amir Goldstein

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='CAJfpegtMvjEjC7B4JpnjyYxzbY=pbW_ATKkKCkjKEsQqzxqqNg@mail.gmail.com' \
    --to=miklos@szeredi.hu \
    --cc=amir73il@gmail.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-unionfs@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=vgoyal@redhat.com \
    --cc=viro@zeniv.linux.org.uk \
    /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).