From: Al Viro <viro@ZenIV.linux.org.uk>
To: Vasiliy Kulikov <segooon@gmail.com>
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: check capabilities in open()
Date: Sat, 24 Jul 2010 18:23:56 +0000 [thread overview]
Message-ID: <20100724182355.GA9134@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20100724160701.GA4907@albatros>
On Sat, Jul 24, 2010 at 08:07:01PM +0400, Vasiliy Kulikov wrote:
> Hi,
>
> I've found that some drivers check process capabilities via capable() in
> open(), not in ioctl()/write()/etc.
>
> I cannot find answer in POSIX, but IMO process expects that file
> descriptors of priviledged user and file descriptors of the same
> file/device are the same in priviledge aspect. Driver should deny/allow
> open() and deny/allow ioctl() based on user priviledges. The path how
> the process gained this fd doesn't matter.
>
> So I think these 2 examples should be equal:
>
> 1) root process opened the file and then dropped its priviledges
>
> 2) nonroot process opened the file
They most certainly should _not_. Consider the following mechanism:
process A authenticates itself to process B
B is convinced to open a file that wouldn't be readable for A.
B passes descriptor to A.
A reads from it.
You are breaking that.
next prev parent reply other threads:[~2010-07-24 18:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-24 16:07 check capabilities in open() Vasiliy Kulikov
2010-07-24 18:23 ` Al Viro [this message]
2010-07-25 5:45 ` Vasiliy Kulikov
2010-07-25 9:23 ` Vasiliy Kulikov
2010-07-26 11:23 ` Ted Ts'o
2010-07-26 16:52 ` Vasiliy Kulikov
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