On Mon, 9 Sep 2024 08:48:14 -0400 Sasha Levin sashal@kernel.org wrote:

This is a note to let you know that I've just added the patch titled

rust: macros: provide correct provenance when constructing THIS_MODULE

to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: rust-macros-provide-correct-provenance-when-construc.patch and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

Hi Sasha,

The `Opaque` type doesn't exist yet in 6.1, so this patch should not be applied to it.

Best, Gary

commit 5b320b29ddf985d8de92c3afa9aebe13ecd5cfad Author: Boqun Feng boqun.feng@gmail.com Date: Wed Aug 28 11:01:29 2024 -0700

rust: macros: provide correct provenance when constructing THIS_MODULE

[ Upstream commit a5a3c952e82c1ada12bf8c55b73af26f1a454bd2 ] Currently while defining `THIS_MODULE` symbol in `module!()`, the pointer used to construct `ThisModule` is derived from an immutable reference of `__this_module`, which means the pointer doesn't have the provenance for writing, and that means any write to that pointer is UB regardless of data races or not. However, the usage of `THIS_MODULE` includes passing this pointer to functions that may write to it (probably in unsafe code), and this will create soundness issues. One way to fix this is using `addr_of_mut!()` but that requires the unstable feature "const_mut_refs". So instead of `addr_of_mut()!`, an extern static `Opaque` is used here: since `Opaque<T>` is transparent to `T`, an extern static `Opaque` will just wrap the C symbol (defined in a C compile unit) in an `Opaque`, which provides a pointer with writable provenance via `Opaque::get()`. This fix the potential UBs because of pointer provenance unmatched. Reported-by: Alice Ryhl aliceryhl@google.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Trevor Gross tmgross@umich.edu Reviewed-by: Benno Lossin benno.lossin@proton.me Reviewed-by: Gary Guo gary@garyguo.net Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/465412664 Fixes: 1fbde52bde73 ("rust: add `macros` crate") Cc: stable@vger.kernel.org # 6.6.x: be2ca1e03965: ("rust: types: Make Opaque::get const") Link: https://lore.kernel.org/r/20240828180129.4046355-1-boqun.feng@gmail.com [ Fixed two typos, reworded title. - Miguel ] Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org

diff --git a/rust/macros/module.rs b/rust/macros/module.rs index 031028b3dc41..071b96639a2e 100644 --- a/rust/macros/module.rs +++ b/rust/macros/module.rs @@ -183,7 +183,11 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream { // freed until the module is unloaded. #[cfg(MODULE)] static THIS_MODULE: kernel::ThisModule = unsafe {{

•            kernel::ThisModule::from_ptr(&kernel::bindings::__this_module as *const _ as *mut _)
  

•            extern \"C\" {{
  

•                static __this_module: kernel::types::Opaque<kernel::bindings::module>;
  

•            }}
  

•            kernel::ThisModule::from_ptr(__this_module.get())
         }};
         #[cfg(not(MODULE))]
         static THIS_MODULE: kernel::ThisModule = unsafe {{