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| author | Boqun Feng <boqun.feng@gmail.com> | 2024-10-12 02:12:28 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-17 16:22:24 +0300 |
| commit | 2d07a38ec94d2d1bd4196d96b9b937cd0e396fee (patch) | |
| tree | ef6942f81e9f5dce02286b475c43e70823fa5d8b | |
| parent | ff5e0f895315706e4ca5a19df15be6866cee4f5d (diff) | |
| download | linux-2d07a38ec94d2d1bd4196d96b9b937cd0e396fee.tar.xz | |
rust: macros: provide correct provenance when constructing THIS_MODULE
commit a5a3c952e82c1ada12bf8c55b73af26f1a454bd2 upstream.
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>
[ Boqun: Use `UnsafeCell` since `Opaque` is not in v6.1, as suggested by
Gary Guo, `UnsafeCell` also suffices for this particular case because
`__this_module` is only used to create `THIS_MODULE`, no other Rust
code will touch it. ]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | rust/macros/module.rs | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/rust/macros/module.rs b/rust/macros/module.rs index 031028b3dc41..94a92ab82b6b 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: core::cell::UnsafeCell<kernel::bindings::module>; + }} + + kernel::ThisModule::from_ptr(__this_module.get()) }}; #[cfg(not(MODULE))] static THIS_MODULE: kernel::ThisModule = unsafe {{ |