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Message-ID: <Zh6wTDoMgvjJZ7T9@boqun-archlinux>
Date: Tue, 16 Apr 2024 10:07:24 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc: Benno Lossin <benno.lossin@...ton.me>, Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Andreas Hindborg <a.hindborg@...sung.com>,
Alice Ryhl <aliceryhl@...gle.com>,
Martin Rodriguez Reboredo <yakoyoku@...il.com>,
Asahi Lina <lina@...hilina.net>,
Sumera Priyadarsini <sylphrenadin@...il.com>,
Neal Gompa <neal@...pa.dev>,
Thomas Bertschinger <tahbertschinger@...il.com>,
Andrea Righi <andrea.righi@...onical.com>,
Matthew Bakhtiari <dev@...k.me>,
Adam Bratschi-Kaye <ark.email@...il.com>, stable@...r.kernel.org,
Masahiro Yamada <masahiroy@...nel.org>,
Wedson Almeida Filho <wedsonaf@...gle.com>,
Finn Behrens <me@...enk.dev>, rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rust: macros: fix soundness issue in `module!` macro
On Sun, Apr 07, 2024 at 10:02:35PM +0200, Miguel Ojeda wrote:
> On Mon, Apr 1, 2024 at 8:53 PM Benno Lossin <benno.lossin@...ton.me> wrote:
> >
> > The `module!` macro creates glue code that are called by C to initialize
> > the Rust modules using the `Module::init` function. Part of this glue
> > code are the local functions `__init` and `__exit` that are used to
> > initialize/destroy the Rust module.
> > These functions are safe and also visible to the Rust mod in which the
> > `module!` macro is invoked. This means that they can be called by other
> > safe Rust code. But since they contain `unsafe` blocks that rely on only
> > being called at the right time, this is a soundness issue.
> >
> > Wrap these generated functions inside of two private modules, this
> > guarantees that the public functions cannot be called from the outside.
> > Make the safe functions `unsafe` and add SAFETY comments.
> >
> > Cc: stable@...r.kernel.org
> > Closes: https://github.com/Rust-for-Linux/linux/issues/629
> > Fixes: 1fbde52bde73 ("rust: add `macros` crate")
> > Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
>
> [ Capitalized comments, avoided newline in non-list SAFETY comments
> and reworded to add Reported-by and newline. ]
>
> Applied to `rust-fixes` -- thanks everyone!
>
As reported by Dirk Behme:
https://rust-for-linux.zulipchat.com/#narrow/stream/291565-Help/topic/How.20to.20use.20THIS_MODULE.20with.20.22.20rust.3A.20macros.3A.20fix.20soundness.20.2E.22/near/433512583
The following is needed to allow modules using `THIS_MODULE` as a static
variable. That being said, maybe we can merge this patch as it is, since
it doesn't break mainline, and the following change can be done in a
separate patch.
Regards,
Boqun
----------------------------->8
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index 293beca0a583..0664b957a70a 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -199,6 +199,17 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
/// Used by the printing macros, e.g. [`info!`].
const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
+ // SAFETY: `__this_module` is constructed by the kernel at load time and will not be
+ // 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 _)
+ }};
+ #[cfg(not(MODULE))]
+ static THIS_MODULE: kernel::ThisModule = unsafe {{
+ kernel::ThisModule::from_ptr(core::ptr::null_mut())
+ }};
+
// Double nested modules, since then nobody can access the public items inside.
mod __module_init {{
mod __module_init {{
@@ -215,17 +226,6 @@ mod __module_init {{
static mut __MOD: Option<{type_}> = None;
- // SAFETY: `__this_module` is constructed by the kernel at load time and will not be
- // 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 _)
- }};
- #[cfg(not(MODULE))]
- static THIS_MODULE: kernel::ThisModule = unsafe {{
- kernel::ThisModule::from_ptr(core::ptr::null_mut())
- }};
-
// Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
/// # Safety
///
@@ -301,7 +301,7 @@ mod __module_init {{
///
/// This function must only be called once.
unsafe fn __init() -> core::ffi::c_int {{
- match <{type_} as kernel::Module>::init(&THIS_MODULE) {{
+ match <{type_} as kernel::Module>::init(&super::super::THIS_MODULE) {{
Ok(m) => {{
// SAFETY:
// no data race, since `__MOD` can only be accessed by this module and
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