linux-kernel - Re: [PATCH] fcntl.h: define AT

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Date:	Mon, 19 Apr 2010 22:20:13 +0000 (UTC)
From:	daw@...berkeley.edu (David Wagner)
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fcntl.h: define AT_EACCESS

Can you share some justification why it's worth extending
faccessat() with new options?

Isn't faccessat() insecure in most use cases, due to TOCTTOU
(time-of-check to time-of-use) vulnerabilities?  When faccessat()
returns 0, you learn that at some point in the past, the process had
permission to access a given file, though the process may or may not
have permission at the moment.  Why is that a useful thing to know?

I'm sure you're familiar with all the standard arguments why using
access() tends to represent a security vulnerability.  Is there a reason
why similar arguments do not apply to faccessat()?
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