From: Matthew Wilcox <willy@infradead.org>
To: Drew DeVault <sir@cmpwn.com>
Cc: linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
Aleksa Sarai <cyphar@cyphar.com>
Subject: Re: [RFC PATCH] fs: introduce mkdirat2 syscall for atomic mkdir
Date: Sun, 28 Feb 2021 02:24:40 +0000 [thread overview]
Message-ID: <20210228022440.GN2723601@casper.infradead.org> (raw)
In-Reply-To: <20210228002500.11483-1-sir@cmpwn.com>
On Sat, Feb 27, 2021 at 07:25:00PM -0500, Drew DeVault wrote:
> The mkdir and mkdirat syscalls both return 0 on success, and use of the
> newly-created directory requires a separate open or openat (or openat2)
> call. The time between these syscalls is an opportunity for a race
> condition. It is thus desirable to establish a means of creating a
> directory and returning an open dirfd for it in one atomic operation.
I don't understand what the TOCTOU race is.
$ cd /tmp
$ mkdir foo
$ sudo su fake
$ rmdir foo
rmdir: failed to remove 'foo': Operation not permitted
$ mv foo bar
mv: cannot move 'foo' to 'bar': Operation not permitted
Where's the problem? If mkdir succeeds in a sticky directory, others
can't remove or rename it. So how can an app be tricked into doing
something wrong?
next prev parent reply other threads:[~2021-02-28 2:25 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-28 0:25 [RFC PATCH] fs: introduce mkdirat2 syscall for atomic mkdir Drew DeVault
2021-02-28 2:13 ` Al Viro
2021-02-28 2:21 ` Drew DeVault
2021-02-28 2:58 ` Al Viro
2021-02-28 13:56 ` Drew DeVault
2021-03-01 19:02 ` J. Bruce Fields
2021-03-08 13:50 ` Stefan Metzmacher
2021-02-28 2:24 ` Matthew Wilcox [this message]
2021-02-28 2:26 ` Drew DeVault
2021-02-28 4:03 ` Matthew Wilcox
2021-02-28 13:57 ` Drew DeVault
2021-03-01 19:09 ` J. Bruce Fields
2021-03-01 19:35 ` Matthew Wilcox
2021-03-01 20:10 ` J. Bruce Fields
2021-03-02 8:24 ` Miklos Szeredi
2021-03-02 7:13 ` Amir Goldstein
2021-03-03 2:39 ` Aleksa Sarai
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