[PATCH v3 0/4] Untrusted Data API

[Benno Lossin <benno.lossin@proton.me>]

Sorry for taking so long with this, I didn't find enough time to work on
this and when I did, I spent a lot of time on trying to get the
interface into a satisfying state. But I always found something that I
didn't like or something that didn't fit correctly. I blame my lack of
knowledge about "all the ways of reading bytes in the kernel" together
with "how should reading bytes in the kernel look like in Rust" for
that. I think it's best I leave the ivory tower behind and just
implement the part that I'm confident about (it's not a lot :) and then
just roll with the use-cases from there. I should've decided to do that
much earlier.

I did manage to create a very basic validation API that I *think* is on
the correct path, but I still marked it as an RFC just to be sure.

We can & should merge the first two patches, as they allow new APIs to
already use `Untrusted` where possible. (some APIs might of course need
to wait for the validation API)

The first use case is Alice's `struct iov_iter` series [1]. It simply
reads untrusted data and then writes it back into userspace without
looking at it. The RFC patch introducing that can either become a normal
patch or be folded into Alice's series.

@Sima: Since you also were pretty enthusiastic about this patch series,
would you mind giving me some pointers to branches/patch series that
have your use-cases for this API? That way I hope to have a better time
designing the validation part.

[1]: https://lore.kernel.org/all/20250311-iov-iter-v1-0-f6c9134ea824@google.com

---
Cheers,
Benno

Benno Lossin (4):
  rust: transmute: add `cast_slice[_mut]` functions
  rust: create basic untrusted data API
  rust: validate: add `Validate` trait
  rust: iov: use untrusted data API

 rust/kernel/iov.rs               |  25 ++--
 rust/kernel/lib.rs               |   1 +
 rust/kernel/transmute.rs         |  41 +++++++
 rust/kernel/validate.rs          | 201 +++++++++++++++++++++++++++++++
 samples/rust/rust_misc_device.rs |   5 +-
 5 files changed, 263 insertions(+), 10 deletions(-)
 create mode 100644 rust/kernel/validate.rs


base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
-- 
2.48.1