Re: Compat 32-bit syscall entry from 64-bit task!? [was: Re:[RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF]

[Eric Paris]

On Tue, 2012-01-17 at 22:25 -0800, Linus Torvalds wrote:

> Of course, limiting things so that you cannot map the same page
> executably *and* writably is one solution - and a good idea regardless
> - so secure environments can still exist. But even then you could have
> races in a multi-threaded environment (they'd just be *much* harder to
> trigger for an attacker).

Gratuitous SELinux for the win e-mail!  (Feel free to delete now)  We
typically, for all confined domains, do not allow mapping anonymous
memory both W and X.  Actually you can't even map it W and then map it
X...

Now if there is file which you have both W and X SELinux permissions
(which is rare, but not impossible) you could map it in two places.  So
we can (and do) build SELinux sandboxes which address this.

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