From: daw@cs.berkeley.edu (David Wagner)
To: linux-kernel@vger.kernel.org
Subject: Re: SECURITY PROBLEM: filesystem permiossion bypass on FD already opened
Date: Fri, 23 Oct 2009 22:55:57 +0000 (UTC) [thread overview]
Message-ID: <hbtc9t$629$1@taverner.cs.berkeley.edu> (raw)
In-Reply-To: 4AE20B6F.4060606@ntd.homelinux.org
NiTRo wrote:
> Just discovered this security problem [...]
>If a FD is opened on a allowed file and then the permission is changed
>the file is still redeable starting from the already read position to
>the EOF.
This is not a security problem; this is Unix working as designed.
That's how file descriptors work. File permissions are checked when
the file is opened, not on every read/write to the file descriptor.
That's a pretty fundamental aspect of how Unix works, and it is
well-documented and well-understood.
On the other hand, the /proc attack that Pavel explains *is* a
security problem. But that's different.
next prev parent reply other threads:[~2009-10-23 22:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-23 20:00 SECURITY PROBLEM: filesystem permiossion bypass on FD already opened NiTRo
2009-10-23 20:44 ` Marcin Slusarz
2009-10-23 20:54 ` Pavel Machek
2009-10-23 22:42 ` NiTRo
2009-10-23 20:59 ` Pavel Machek
2009-10-23 22:55 ` David Wagner [this message]
2009-10-25 6:30 ` Pavel Machek
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