From: Robert Hancock <hancockr@shaw.ca>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Rodolfo Giometti <giometti@enneenne.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] LinuxPPS (with new syscalls API)
Date: Tue, 26 Jun 2007 17:33:28 -0600 [thread overview]
Message-ID: <4681A248.6070109@shaw.ca> (raw)
In-Reply-To: <fa.RLNIoDXtVxFnlYMPJh2Q2+yDDOk@ifi.uio.no>
David Woodhouse wrote:
> On Tue, 2007-06-26 at 19:06 +0200, Rodolfo Giometti wrote:
>> On Tue, Jun 26, 2007 at 11:57:07AM +0100, David Woodhouse wrote:
>>> Your syscalls blindly dereference userspace pointers instead of using
>>> copy_{to,from} user.
>> I use access_ok() to test userspace addresses. It should be ok,
>> shouldn't it?
>
> No; it's racy. You must use copy_from_user() and copy_to_user().
Not only is it racy, but it doesn't even do all of the checks that
copy_to/from_user does. access_ok only validates that the region given
is potentially valid, not that it actually is. Using access_ok only
allows you to use __copy_to/from_user instead, which skips the same
checks that access_ok does - not worth it unless you do repeated copies
to/from the same region of memory.
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/
next parent reply other threads:[~2007-06-26 23:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <fa.KzVWiacZsGdGiMxLldFOOPOdIEw@ifi.uio.no>
[not found] ` <fa.TdDfr0FpGG8OjqtqWj6RNRusuU0@ifi.uio.no>
[not found] ` <fa.qT2j8q7/hQ2xVpeJCg7VGv+FvpI@ifi.uio.no>
[not found] ` <fa.RLNIoDXtVxFnlYMPJh2Q2+yDDOk@ifi.uio.no>
2007-06-26 23:33 ` Robert Hancock [this message]
2007-06-26 10:06 [PATCH] LinuxPPS (with new syscalls API) Rodolfo Giometti
2007-06-26 10:57 ` David Woodhouse
2007-06-26 17:06 ` Rodolfo Giometti
2007-06-26 17:38 ` David Woodhouse
2007-06-26 18:13 ` Rodolfo Giometti
2007-06-26 18:20 ` David Woodhouse
2007-06-27 10:14 ` Rodolfo Giometti
2007-06-27 10:18 ` David Woodhouse
2007-06-27 12:58 ` Rodolfo Giometti
2007-06-27 16:11 ` David Woodhouse
2007-06-27 17:45 ` Rodolfo Giometti
2007-06-27 17:49 ` David Woodhouse
2007-06-27 22:46 ` Rodolfo Giometti
2007-06-28 8:08 ` David Woodhouse
2007-06-28 8:15 ` Rodolfo Giometti
2007-06-28 8:31 ` David Woodhouse
2007-06-28 8:40 ` Rodolfo Giometti
2007-06-28 11:44 ` David Woodhouse
2007-06-28 14:15 ` Rodolfo Giometti
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