On 06/01/2016 07:17 PM, Dave Hansen wrote:

On 06/01/2016 05:11 PM, Michael Kerrisk (man-pages) wrote:

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If I read this right, it doesn't actually remove any pkey restrictions
that may have been applied while the key was allocated.  So there could be
pages with that key assigned that might do surprising things if the key is
reallocated for another use later, right?  Is that how the API is intended
to work?

Yeah, that's how it works.

It's not ideal.  It would be _best_ if we during mm_pkey_free(), we
ensured that no VMAs under that mm have that vma_pkey() set.  But, that
search would be potentially expensive (a walk over all VMAs), or would
force us to keep a data structure with a count of all the VMAs with a
given key.

I should probably discuss this behavior in the manpages and address it

s/probably//

And, did I miss it. Was there an updated man-pages patch in the latest
series? I did not notice it.

There have been to changes to the patches that warranted updating the
manpages until now.  I'll send the update immediately.

Do those updated pages include discussion of the point noted above?
I could not see it mentioned there.

Just by the way, the above behavior seems to offer possibilities
for users to shoot themselves in the foot, in a way that has security
implications. (Or do I misunderstand?)

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/