[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <30F8C3A4-91C8-4043-B236-359D2D0E4A8B@oracle.com>
Date: Mon, 6 Jul 2015 19:17:03 +0100
From: John Haxby <john.haxby@...cle.com>
To: oss-security@...ts.openwall.com
Subject: Re: How serious is undefined behavior?
> On 6 Jul 2015, at 17:17, Hanno Böck <hanno@...eck.de> wrote:
>
> However I wonder how practically relevant these issues are and also
> how much focus should be given to them. Do people have good examples
> where e.g. an invalid shift operation caused a real, severe security
> issue?
> Would people think it's a wise idea to put a lot of effort into testing
> applications with ubsan enabled and reporting all the bugs that pop up?
> (that would mean a lot of bugreports) Or would this be perceived as an
> annoying "that's a theoretical C language nitpick issue and not a real
> bug".
I don't have the example any more, but some years ago(*) we did have a problem because undefined behaviour on one compiler showed up differently on another. In our case it was a hard to track down bug because it wasn't particularly obvious that it was undefined. We were similarly bitten when a new compiler changed the implementation of something else undefined.
And of course, the classic foo(a++, bar(a++)) crops up in one form or another on a regular basis, It may have been that that changed from one release to another: one compiler evaluated all the arguments right to left, another one evaluated the first few left to right (to go into registers) and the later ones right to left. I forget, sorry.
Of course, most of the time these just result in peculiar bugs rather than exploitable security issues, but it's not too hard to come up with plausible cases that would lead to a failing security check.
jch
(*) OpenMail, if anyone wonders or cares.
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
