Re: linux bugs (survival stories)?

[Valdis.Kletnieks () vt edu]

On Tue, 12 Apr 2005 12:06:59 +0545, Bipin Gautam said:

> every to verify its types) On the other hand we have had products like
>  stack guard, lib safe, grsecurity.net, se-linux

> BUT i was woundering, to what extent adding these extra security
> measures are effective against the real attacks & bugs discovered in
> the kernel.

They do almost nothing to guard against bugs discovered *in the kernel*,
because all of them are addressing *userspace* bugs.

There's pretty much *zero* you can do to protect against kernel bugs, other
than audit the code and get rid of the bugs.  Remember it's basically a
monolithic kernel - that means that if a bug lets somebody get control of
the kernel, it's Game Over.

There's a reason why binary kernel modules are frowned upon - and it's precisely
that.  As far as the kernel is concerned, a security bug and a buggy binary module
are the same thing - both can go scribbling on whatever kernel data structures
it wants to, and there's no real way to stop it.

If anybody wants a good kernel-auditing project, just start going through the
2.6.12-rc2 tree and look at uses of copy_from_user(), and make sure that each
use of that function then proceeds to *validate* the data (especially in the
various driver's .ioctl methods - historically a place for issues).   At least
the tree seems to be a lot better with not ignoring the return value of
copy_from_user() ;)

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