From: Christoph Hellwig <hch@lst.de>
To: sishuaigong <sishuai@purdue.edu>
Cc: jlbec@evilplan.org, hch@lst.de, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] configfs: fix a race in configfs_lookup()
Date: Mon, 23 Aug 2021 09:46:36 +0200 [thread overview]
Message-ID: <20210823074636.GA23822@lst.de> (raw)
In-Reply-To: <20210820214458.14087-1-sishuai@purdue.edu>
On Fri, Aug 20, 2021 at 05:44:58PM -0400, sishuaigong wrote:
> When configfs_lookup() is executing list_for_each_entry(),
> it is possible that configfs_dir_lseek() is calling list_del().
> Some unfortunate interleavings of them can cause a kernel NULL
> pointer dereference error
>
> Thread 1 Thread 2
> //configfs_dir_lseek() //configfs_lookup()
> list_del(&cursor->s_sibling);
> list_for_each_entry(sd, ...)
>
> Fix this bug by using list_for_each_entry_safe() instead.
I don't see how list_for_each_entry_safe would save you there.
You need a lock to sychronize the two, list_for_each_entry_safe
only ensures the next entry is looked up before iterating over
the current one.
next prev parent reply other threads:[~2021-08-23 7:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-20 21:44 [PATCH] configfs: fix a race in configfs_lookup() sishuaigong
2021-08-23 7:46 ` Christoph Hellwig [this message]
[not found] ` <AFABA8B1-0523-4F8C-A9DD-DDC5638DEAF7@purdue.edu>
2021-08-23 17:08 ` Christoph Hellwig
2021-08-23 19:07 ` Gong, Sishuai
2021-08-25 5:19 ` Al Viro
2021-08-25 5:29 ` Christoph Hellwig
[not found] <20210820213243.786-1-sishuai@purdue.edu>
2021-12-29 2:23 ` Gong, Sishuai
-- strict thread matches above, loose matches on Subject: below --
2023-09-02 20:20 Kyle Zeng
2023-09-02 21:08 ` Greg KH
2023-09-02 21:55 ` Kyle Zeng
2023-09-03 8:45 ` Greg KH
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