mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: Tejun Heo <tj@kernel.org>
To: "Christian A. Ehrhardt" <lk@c--e.de>
Cc: linux-kernel@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] kernfs: fix use-after-free in __kernfs_remove
Date: Thu, 8 Sep 2022 07:14:43 -1000	[thread overview]
Message-ID: <YxojA7pDe8Ur7wpd@slm.duckdns.org> (raw)
In-Reply-To: <20220907200811.654034-1-lk@c--e.de>

Hello, Christian.

On Wed, Sep 07, 2022 at 10:08:11PM +0200, Christian A. Ehrhardt wrote:
> Concurrent calls to __kernfs_remove can race on the removal
> of the root node: The race occurs if the root node(kn) is freed
> during kernfs_drain. The child node(pos) is explicitly protected
> with an additional ref count. Do the same for the root node.

I don't think this is right. We don't support parallel invocations of
__kernfs_remove() this way. If @kn can be freed during kernfs_drain(), it
also means that it can be freed before kernfs_rwsem is grabbed in
kernfs_remove(). The caller must be responsible for ensuring that @kn
remains allocated. Otherwise, it can't be made reliable.

Thanks.

-- 
tejun

  reply	other threads:[~2022-09-08 17:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-07 20:08 Christian A. Ehrhardt
2022-09-08 17:14 ` Tejun Heo [this message]
2022-09-08 22:25   ` Christian A. Ehrhardt
2022-09-12 21:24     ` Christian A. Ehrhardt
2022-09-12 21:39       ` Tejun Heo
2022-09-13 12:17         ` [PATCH v2] " Christian A. Ehrhardt
2022-09-19 17:35           ` Tejun Heo

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=YxojA7pDe8Ur7wpd@slm.duckdns.org \
    --to=tj@kernel.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=lk@c--e.de \
    /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
all inboxes | Powered by JetHome®