Messages in this thread | | | Date | Wed, 5 May 2021 12:08:06 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v18 0/9] mm: introduce memfd_secret system call to create "secret" memory areas |
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On Wed, 3 Mar 2021 18:22:00 +0200 Mike Rapoport <rppt@kernel.org> wrote:
> This is an implementation of "secret" mappings backed by a file descriptor. > > The file descriptor backing secret memory mappings is created using a > dedicated memfd_secret system call The desired protection mode for the > memory is configured using flags parameter of the system call. The mmap() > of the file descriptor created with memfd_secret() will create a "secret" > memory mapping. The pages in that mapping will be marked as not present in > the direct map and will be present only in the page table of the owning mm. > > Although normally Linux userspace mappings are protected from other users, > such secret mappings are useful for environments where a hostile tenant is > trying to trick the kernel into giving them access to other tenants > mappings.
I continue to struggle with this and I don't recall seeing much enthusiasm from others. Perhaps we're all missing the value point and some additional selling is needed.
Am I correct in understanding that the overall direction here is to protect keys (and perhaps other things) from kernel bugs? That if the kernel was bug-free then there would be no need for this feature? If so, that's a bit sad. But realistic I guess.
Is this intended to protect keys/etc after the attacker has gained the ability to run arbitrary kernel-mode code? If so, that seems optimistic, doesn't it?
I think that a very complete description of the threats which this feature addresses would be helpful.
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