Re: [PATCH] capability: WARN when invalid capability is requested rather than BUG/panic

On Tue, 2008-09-30 at 11:28 -0500, Serge E. Hallyn wrote:
Quoting Eric Paris (eparis@xxxxxxxxxx):

Perhaps we should have CAP_TO_INDEX mask itself?

#define CAP_TO_INDEX(x) (((x) >> 5) & _KERNEL_CAPABILITY_U32S)

Well, you save a branch and won't get the pagefault so it does 'fix' the
pagefault/panic from cap code. It doesn't tell us when others screw up
and SELinux is still possibly going to BUG(). We are also going to
actually be returning a permission decision not on what was requested
but on something wholely different.

So exactly what was requested?

A capability that they cannot possibly have since it doesn't exist :)

I like mine better, but I'm ok with yours and can just do my changes in
SELinux if this is how cap wants to handle it. I don't really like the

Heh I don't like either one, just thought this would reduce the overhead
a bit :)

No argument from me that patching up for buggy drivers sucks. Yours
would be less overhead, and it would return the cap system back to
pre-2.6.25 operation (garbage in garbage out but no panic). Since we
already have the branch in SELinux its no 'extra' overhead to EPERM
there instead of here (garbage in EPERM out).

-Eric

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