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SubjectRe: [PATCH] mm/mincore: allow for making sys_mincore() privileged
On Sat, 5 Jan 2019, Linus Torvalds wrote:

> > There are possibilities [1] how mincore() could be used as a converyor of
> > a sidechannel information about pagecache metadata.
>
> Can we please just limit it to vma's that are either anonymous, or map
> a file that the user actually owns?
>
> Then the capability check could be for "override the file owner check"
> instead, which makes tons of sense.

Makes sense.

I am still not completely sure what to return in such cases though; we can
either blatantly lie and always pretend that the pages are resident (to
avoid calling process entering some prefaulting mode), or return -ENOMEM
for mappings of files that don't belong to the user (in case it's not
CAP_SYS_ADMIN one).

--
Jiri Kosina
SUSE Labs

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