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SubjectRe: [announce] [patch] NX (No eXecute) support for x86, 2.6.7-rc2-bk2
Andi Kleen wrote:

>>The whole point of NX, though, is that it prevents certain classes of
>>exploits. If a setuid binary is vulnerable to one of these, then Ingo's
>>patch "fixes" it. Your approach breaks that.
>
>
> Good point.
>
> But that only applies to the NX personality bit. For the uname emulation
> it is not an issue.
>
> So maybe the dropping on exec should only zero a few selected
> personality bits, but not all.

True.

>>I don't like Ingo's fix either, though. At least it should check
>>CAP_PTRACE or some such. A better fix would be for LSM to pass down a flag
>>indicating a change of security context. I'll throw that in to my
>>caps/apply_creds cleanup, in case that ever gets applied.
>
>
> Don't think we should require an LSM module for that. That's
> far overkill.

I'm not suggesting a new LSM module. I'm suggesting modifying the existing
LSM code to handle this cleanly. We already have a function
(security_bprm_secureexec) that does something like this, and, in fact,
it's probably the right thing to test here.

I'm currently compiling a new patch (modified from my last caps cleanup)
that makes a new bitfield for this stuff. I don't know if it's worth
applying, but I'll send it off to Andrew once I convince myself it works.

--Andy

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