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Boqun Feng
a5a3c952e8
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 <[email protected]> Signed-off-by: Boqun Feng <[email protected]> Reviewed-by: Alice Ryhl <[email protected]> Reviewed-by: Trevor Gross <[email protected]> Reviewed-by: Benno Lossin <[email protected]> Reviewed-by: Gary Guo <[email protected]> Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/465412664 Fixes:1fbde52bde("rust: add `macros` crate") Cc: [email protected] # 6.6.x:be2ca1e039: ("rust: types: Make Opaque::get const") Link: https://lore.kernel.org/r/[email protected] [ Fixed two typos, reworded title. - Miguel ] Signed-off-by: Miguel Ojeda <[email protected]>