Re: [patch 0/5] Support for sanitization flag in low-level page allocator

[Rik van Riel]

Peter Zijlstra wrote:

> Seems like a particularly wasteful use of a pageflag. Why not simply
> erase the buffer before freeing in those few places where we know its
> important (ie. exactly those places you now put the pageflag in)?

You don't always know this at page free time.

I could see the PG_sensitive flag being used from
userspace through mmap or madvise flags.  This way
the sensitive memory from a program like gpg would
be cleaned, even if gpg died in a segfault accident.

I could also imagine the suspend-to-disk code skipping
PG_sensitive pages when storing data to disk, and
replacing it with some magic signature so programs
that use special PG_sensitive buffers can know that
their crypto key disappeared after a restore.

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