FAILED: patch "[PATCH] rust: macros: provide correct provenance when constructing" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x a5a3c952e82c1ada12bf8c55b73af26f1a454bd2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024090831-camera-backlands-a643@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

a5a3c952e82c ("rust: macros: provide correct provenance when constructing THIS_MODULE")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a5a3c952e82c1ada12bf8c55b73af26f1a454bd2 Mon Sep 17 00:00:00 2001
From: Boqun Feng <boqun.feng@gmail.com>
Date: Wed, 28 Aug 2024 11:01:29 -0700
Subject: [PATCH] rust: macros: provide correct provenance when constructing
 THIS_MODULE

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>

diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 411dc103d82e..7a5b899e47b7 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -217,7 +217,11 @@ 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 {{